File Coverage

blib/lib/Ekoi8u.pm

Criterion	Covered	Total	%
statement	905	2814	32.1
branch	890	2412	36.9
condition	98	355	27.6
subroutine	54	113	47.7
pod	7	74	9.4
total	1954	5768	33.8

package Ekoi8u;
use strict;
BEGIN { $INC{'warnings.pm'} = '' if $] < 5.006 } use warnings;
######################################################################
#
# Ekoi8u - Run-time routines for KOI8U.pm
#
# http://search.cpan.org/dist/Char-KOI8U/
#
# Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2018, 2019 INABA Hitoshi
######################################################################

use 5.00503;    # Galapagos Consensus 1998 for primetools
# use 5.008001; # Lancaster Consensus 2013 for toolchains

# 12.3. Delaying use Until Runtime
# in Chapter 12. Packages, Libraries, and Modules
# of ISBN 0-596-00313-7 Perl Cookbook, 2nd Edition.
# (and so on)

# Version numbers should be boring
# http://www.dagolden.com/index.php/369/version-numbers-should-be-boring/
# For the impatient, the disinterested or those who just want to follow
# a recipe, my advice for all modules is this:
# our $VERSION = "0.001"; # or "0.001_001" for a dev release
# $VERSION = eval $VERSION; # No!! because '1.10' makes '1.1'

use vars qw($VERSION);
$VERSION = '1.22';
$VERSION = $VERSION;

BEGIN {
    if ($^X =~ / jperl /oxmsi) {
        die __FILE__, ": needs perl(not jperl) 5.00503 or later. (\$^X==$^X)\n";
    }
    if (CORE::ord('A') == 193) {
        die __FILE__, ": is not US-ASCII script (may be EBCDIC or EBCDIK script).\n";
    }
    if (CORE::ord('A') != 0x41) {
        die __FILE__, ": is not US-ASCII script (must be US-ASCII script).\n";
    }
}

BEGIN {

    # instead of utf8.pm
    CORE::eval q{
        no warnings qw(redefine);
        *utf8::upgrade   = sub { CORE::length $_[0] };
        *utf8::downgrade = sub { 1 };
        *utf8::encode    = sub {   };
        *utf8::decode    = sub { 1 };
        *utf8::is_utf8   = sub {   };
        *utf8::valid     = sub { 1 };
    };
    if ($@) {
        *utf8::upgrade   = sub { CORE::length $_[0] };
        *utf8::downgrade = sub { 1 };
        *utf8::encode    = sub {   };
        *utf8::decode    = sub { 1 };
        *utf8::is_utf8   = sub {   };
        *utf8::valid     = sub { 1 };
    }
}

# instead of Symbol.pm
BEGIN {
    sub gensym () {
        if ($] < 5.006) {
            return \do { local *_ };
        }
        else {
            return undef;
        }
    }

    sub qualify ($$) {
        my($name) = @_;

        if (ref $name) {
            return $name;
        }
        elsif (Ekoi8u::index($name,'::') >= 0) {
            return $name;
        }
        elsif (Ekoi8u::index($name,"'") >= 0) {
            return $name;
        }

        # special character, "^xyz"
        elsif ($name =~ /\A \^ [ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_]+ \z/x) {

            # RGS 2001-11-05 : translate leading ^X to control-char
            $name =~ s{\A \^ ([ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_]) }{'qq(\c'.$1.')'}xee;
            return 'main::' . $name;
        }

        # Global names
        elsif ($name =~ /\A (?: ARGV | ARGVOUT | ENV | INC | SIG | STDERR | STDIN | STDOUT ) \z/x) {
            return 'main::' . $name;
        }

        # or other
        elsif ($name =~ /\A [^ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz] \z/x) {
            return 'main::' . $name;
        }

        elsif (defined $_[1]) {
            return $_[1] . '::' . $name;
        }
        else {
            return (caller)[0] . '::' . $name;
        }
    }

    sub qualify_to_ref ($;$) {
        if (defined $_[1]) {
            no strict qw(refs);
            return \*{ qualify $_[0], $_[1] };
        }
        else {
            no strict qw(refs);
            return \*{ qualify $_[0], (caller)[0] };
        }
    }
}

# P.714 29.2.39. flock
# in Chapter 29: Functions
# of ISBN 0-596-00027-8 Programming Perl Third Edition.

# P.863 flock
# in Chapter 27: Functions
# of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

sub LOCK_SH() {1}
sub LOCK_EX() {2}
sub LOCK_UN() {8}
sub LOCK_NB() {4}

# instead of Carp.pm
sub carp;
sub croak;
sub cluck;
sub confess;

# 6.18. Matching Multiple-Byte Characters
# in Chapter 6. Pattern Matching
# of ISBN 978-1-56592-243-3 Perl Perl Cookbook.
# (and so on)

# regexp of character
my $your_char = q{[\x00-\xFF]};
use vars qw($qq_char); $qq_char = qr/\\c[\x40-\x5F]|\\?(?:$your_char)/oxms;
use vars qw($q_char);  $q_char  = qr/$your_char/oxms;

#
# KOI8-U character range per length
#
my %range_tr = ();

#
# KOI8-U case conversion
#
my %lc = ();
@lc{qw(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z)} =
    qw(a b c d e f g h i j k l m n o p q r s t u v w x y z);
my %uc = ();
@uc{qw(a b c d e f g h i j k l m n o p q r s t u v w x y z)} =
    qw(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z);
my %fc = ();
@fc{qw(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z)} =
    qw(a b c d e f g h i j k l m n o p q r s t u v w x y z);

if (0) {
}

elsif (__PACKAGE__ =~ / \b Ekoi8u \z/oxms) {
    %range_tr = (
        1 => [ [0x00..0xFF],
             ],
    );

    %lc = (%lc,
        "\xB3" => "\xA3",     # CYRILLIC LETTER IO
        "\xB4" => "\xA4",     # CYRILLIC LETTER UKRAINIAN IE
        "\xB6" => "\xA6",     # CYRILLIC LETTER BYELORUSSIAN-UKRAINIAN I
        "\xB7" => "\xA7",     # CYRILLIC LETTER YI (UKRAINIAN)
        "\xBD" => "\xAD",     # CYRILLIC LETTER GHE WITH UPTURN
        "\xE0" => "\xC0",     # CYRILLIC LETTER YU
        "\xE1" => "\xC1",     # CYRILLIC LETTER A
        "\xE2" => "\xC2",     # CYRILLIC LETTER BE
        "\xE3" => "\xC3",     # CYRILLIC LETTER TSE
        "\xE4" => "\xC4",     # CYRILLIC LETTER DE
        "\xE5" => "\xC5",     # CYRILLIC LETTER IE
        "\xE6" => "\xC6",     # CYRILLIC LETTER EF
        "\xE7" => "\xC7",     # CYRILLIC LETTER GHE
        "\xE8" => "\xC8",     # CYRILLIC LETTER KHA
        "\xE9" => "\xC9",     # CYRILLIC LETTER I
        "\xEA" => "\xCA",     # CYRILLIC LETTER SHORT I
        "\xEB" => "\xCB",     # CYRILLIC LETTER KA
        "\xEC" => "\xCC",     # CYRILLIC LETTER EL
        "\xED" => "\xCD",     # CYRILLIC LETTER EM
        "\xEE" => "\xCE",     # CYRILLIC LETTER EN
        "\xEF" => "\xCF",     # CYRILLIC LETTER O
        "\xF0" => "\xD0",     # CYRILLIC LETTER PE
        "\xF1" => "\xD1",     # CYRILLIC LETTER YA
        "\xF2" => "\xD2",     # CYRILLIC LETTER ER
        "\xF3" => "\xD3",     # CYRILLIC LETTER ES
        "\xF4" => "\xD4",     # CYRILLIC LETTER TE
        "\xF5" => "\xD5",     # CYRILLIC LETTER U
        "\xF6" => "\xD6",     # CYRILLIC LETTER ZHE
        "\xF7" => "\xD7",     # CYRILLIC LETTER VE
        "\xF8" => "\xD8",     # CYRILLIC LETTER SOFT SIGN
        "\xF9" => "\xD9",     # CYRILLIC LETTER YERU
        "\xFA" => "\xDA",     # CYRILLIC LETTER ZE
        "\xFB" => "\xDB",     # CYRILLIC LETTER SHA
        "\xFC" => "\xDC",     # CYRILLIC LETTER E
        "\xFD" => "\xDD",     # CYRILLIC LETTER SHCHA
        "\xFE" => "\xDE",     # CYRILLIC LETTER CHE
        "\xFF" => "\xDF",     # CYRILLIC LETTER HARD SIGN
    );

    %uc = (%uc,
        "\xA3" => "\xB3",     # CYRILLIC LETTER IO
        "\xA4" => "\xB4",     # CYRILLIC LETTER UKRAINIAN IE
        "\xA6" => "\xB6",     # CYRILLIC LETTER BYELORUSSIAN-UKRAINIAN I
        "\xA7" => "\xB7",     # CYRILLIC LETTER YI (UKRAINIAN)
        "\xAD" => "\xBD",     # CYRILLIC LETTER GHE WITH UPTURN
        "\xC0" => "\xE0",     # CYRILLIC LETTER YU
        "\xC1" => "\xE1",     # CYRILLIC LETTER A
        "\xC2" => "\xE2",     # CYRILLIC LETTER BE
        "\xC3" => "\xE3",     # CYRILLIC LETTER TSE
        "\xC4" => "\xE4",     # CYRILLIC LETTER DE
        "\xC5" => "\xE5",     # CYRILLIC LETTER IE
        "\xC6" => "\xE6",     # CYRILLIC LETTER EF
        "\xC7" => "\xE7",     # CYRILLIC LETTER GHE
        "\xC8" => "\xE8",     # CYRILLIC LETTER KHA
        "\xC9" => "\xE9",     # CYRILLIC LETTER I
        "\xCA" => "\xEA",     # CYRILLIC LETTER SHORT I
        "\xCB" => "\xEB",     # CYRILLIC LETTER KA
        "\xCC" => "\xEC",     # CYRILLIC LETTER EL
        "\xCD" => "\xED",     # CYRILLIC LETTER EM
        "\xCE" => "\xEE",     # CYRILLIC LETTER EN
        "\xCF" => "\xEF",     # CYRILLIC LETTER O
        "\xD0" => "\xF0",     # CYRILLIC LETTER PE
        "\xD1" => "\xF1",     # CYRILLIC LETTER YA
        "\xD2" => "\xF2",     # CYRILLIC LETTER ER
        "\xD3" => "\xF3",     # CYRILLIC LETTER ES
        "\xD4" => "\xF4",     # CYRILLIC LETTER TE
        "\xD5" => "\xF5",     # CYRILLIC LETTER U
        "\xD6" => "\xF6",     # CYRILLIC LETTER ZHE
        "\xD7" => "\xF7",     # CYRILLIC LETTER VE
        "\xD8" => "\xF8",     # CYRILLIC LETTER SOFT SIGN
        "\xD9" => "\xF9",     # CYRILLIC LETTER YERU
        "\xDA" => "\xFA",     # CYRILLIC LETTER ZE
        "\xDB" => "\xFB",     # CYRILLIC LETTER SHA
        "\xDC" => "\xFC",     # CYRILLIC LETTER E
        "\xDD" => "\xFD",     # CYRILLIC LETTER SHCHA
        "\xDE" => "\xFE",     # CYRILLIC LETTER CHE
        "\xDF" => "\xFF",     # CYRILLIC LETTER HARD SIGN
    );

    %fc = (%fc,
        "\xB3" => "\xA3",     # CYRILLIC CAPITAL LETTER IO                       --> CYRILLIC SMALL LETTER IO
        "\xB4" => "\xA4",     # CYRILLIC CAPITAL LETTER UKRAINIAN IE             --> CYRILLIC SMALL LETTER UKRAINIAN IE
        "\xB6" => "\xA6",     # CYRILLIC CAPITAL LETTER BYELORUSSIAN-UKRAINIAN I --> CYRILLIC SMALL LETTER BYELORUSSIAN-UKRAINIAN I
        "\xB7" => "\xA7",     # CYRILLIC CAPITAL LETTER YI                       --> CYRILLIC SMALL LETTER YI
        "\xBD" => "\xAD",     # CYRILLIC CAPITAL LETTER GHE WITH UPTURN          --> CYRILLIC SMALL LETTER GHE WITH UPTURN
        "\xE0" => "\xC0",     # CYRILLIC CAPITAL LETTER YU                       --> CYRILLIC SMALL LETTER YU
        "\xE1" => "\xC1",     # CYRILLIC CAPITAL LETTER A                        --> CYRILLIC SMALL LETTER A
        "\xE2" => "\xC2",     # CYRILLIC CAPITAL LETTER BE                       --> CYRILLIC SMALL LETTER BE
        "\xE3" => "\xC3",     # CYRILLIC CAPITAL LETTER TSE                      --> CYRILLIC SMALL LETTER TSE
        "\xE4" => "\xC4",     # CYRILLIC CAPITAL LETTER DE                       --> CYRILLIC SMALL LETTER DE
        "\xE5" => "\xC5",     # CYRILLIC CAPITAL LETTER IE                       --> CYRILLIC SMALL LETTER IE
        "\xE6" => "\xC6",     # CYRILLIC CAPITAL LETTER EF                       --> CYRILLIC SMALL LETTER EF
        "\xE7" => "\xC7",     # CYRILLIC CAPITAL LETTER GHE                      --> CYRILLIC SMALL LETTER GHE
        "\xE8" => "\xC8",     # CYRILLIC CAPITAL LETTER HA                       --> CYRILLIC SMALL LETTER HA
        "\xE9" => "\xC9",     # CYRILLIC CAPITAL LETTER I                        --> CYRILLIC SMALL LETTER I
        "\xEA" => "\xCA",     # CYRILLIC CAPITAL LETTER SHORT I                  --> CYRILLIC SMALL LETTER SHORT I
        "\xEB" => "\xCB",     # CYRILLIC CAPITAL LETTER KA                       --> CYRILLIC SMALL LETTER KA
        "\xEC" => "\xCC",     # CYRILLIC CAPITAL LETTER EL                       --> CYRILLIC SMALL LETTER EL
        "\xED" => "\xCD",     # CYRILLIC CAPITAL LETTER EM                       --> CYRILLIC SMALL LETTER EM
        "\xEE" => "\xCE",     # CYRILLIC CAPITAL LETTER EN                       --> CYRILLIC SMALL LETTER EN
        "\xEF" => "\xCF",     # CYRILLIC CAPITAL LETTER O                        --> CYRILLIC SMALL LETTER O
        "\xF0" => "\xD0",     # CYRILLIC CAPITAL LETTER PE                       --> CYRILLIC SMALL LETTER PE
        "\xF1" => "\xD1",     # CYRILLIC CAPITAL LETTER YA                       --> CYRILLIC SMALL LETTER YA
        "\xF2" => "\xD2",     # CYRILLIC CAPITAL LETTER ER                       --> CYRILLIC SMALL LETTER ER
        "\xF3" => "\xD3",     # CYRILLIC CAPITAL LETTER ES                       --> CYRILLIC SMALL LETTER ES
        "\xF4" => "\xD4",     # CYRILLIC CAPITAL LETTER TE                       --> CYRILLIC SMALL LETTER TE
        "\xF5" => "\xD5",     # CYRILLIC CAPITAL LETTER U                        --> CYRILLIC SMALL LETTER U
        "\xF6" => "\xD6",     # CYRILLIC CAPITAL LETTER ZHE                      --> CYRILLIC SMALL LETTER ZHE
        "\xF7" => "\xD7",     # CYRILLIC CAPITAL LETTER VE                       --> CYRILLIC SMALL LETTER VE
        "\xF8" => "\xD8",     # CYRILLIC CAPITAL LETTER SOFT SIGN                --> CYRILLIC SMALL LETTER SOFT SIGN
        "\xF9" => "\xD9",     # CYRILLIC CAPITAL LETTER YERU                     --> CYRILLIC SMALL LETTER YERU
        "\xFA" => "\xDA",     # CYRILLIC CAPITAL LETTER ZE                       --> CYRILLIC SMALL LETTER ZE
        "\xFB" => "\xDB",     # CYRILLIC CAPITAL LETTER SHA                      --> CYRILLIC SMALL LETTER SHA
        "\xFC" => "\xDC",     # CYRILLIC CAPITAL LETTER E                        --> CYRILLIC SMALL LETTER E
        "\xFD" => "\xDD",     # CYRILLIC CAPITAL LETTER SHCHA                    --> CYRILLIC SMALL LETTER SHCHA
        "\xFE" => "\xDE",     # CYRILLIC CAPITAL LETTER CHE                      --> CYRILLIC SMALL LETTER CHE
        "\xFF" => "\xDF",     # CYRILLIC CAPITAL LETTER HARD SIGN                --> CYRILLIC SMALL LETTER HARD SIGN
    );
}

else {
    croak "Don't know my package name '@{[__PACKAGE__]}'";
}

#
# @ARGV wildcard globbing
#
sub import {

    if ($^O =~ /\A (?: MSWin32 | NetWare | symbian | dos ) \z/oxms) {
        my @argv = ();
        for (@ARGV) {

            # has space
            if (/\A (?:$q_char)*? [ ] /oxms) {
                if (my @glob = Ekoi8u::glob(qq{"$_"})) {
                    push @argv, @glob;
                }
                else {
                    push @argv, $_;
                }
            }

            # has wildcard metachar
            elsif (/\A (?:$q_char)*? [*?] /oxms) {
                if (my @glob = Ekoi8u::glob($_)) {
                    push @argv, @glob;
                }
                else {
                    push @argv, $_;
                }
            }

            # no wildcard globbing
            else {
                push @argv, $_;
            }
        }
        @ARGV = @argv;
    }

    *Char::ord           = \&KOI8U::ord;
    *Char::ord_          = \&KOI8U::ord_;
    *Char::reverse       = \&KOI8U::reverse;
    *Char::getc          = \&KOI8U::getc;
    *Char::length        = \&KOI8U::length;
    *Char::substr        = \&KOI8U::substr;
    *Char::index         = \&KOI8U::index;
    *Char::rindex        = \&KOI8U::rindex;
    *Char::eval          = \&KOI8U::eval;
    *Char::escape        = \&KOI8U::escape;
    *Char::escape_token  = \&KOI8U::escape_token;
    *Char::escape_script = \&KOI8U::escape_script;
}

# P.230 Care with Prototypes
# in Chapter 6: Subroutines
# of ISBN 0-596-00027-8 Programming Perl Third Edition.
#
# If you aren't careful, you can get yourself into trouble with prototypes.
# But if you are careful, you can do a lot of neat things with them. This is
# all very powerful, of course, and should only be used in moderation to make
# the world a better place.

# P.332 Care with Prototypes
# in Chapter 7: Subroutines
# of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.
#
# If you aren't careful, you can get yourself into trouble with prototypes.
# But if you are careful, you can do a lot of neat things with them. This is
# all very powerful, of course, and should only be used in moderation to make
# the world a better place.

#
# Prototypes of subroutines
#
sub unimport {}
sub Ekoi8u::split(;$$$);
sub Ekoi8u::tr($$$$;$);
sub Ekoi8u::chop(@);
sub Ekoi8u::index($$;$);
sub Ekoi8u::rindex($$;$);
sub Ekoi8u::lcfirst(@);
sub Ekoi8u::lcfirst_();
sub Ekoi8u::lc(@);
sub Ekoi8u::lc_();
sub Ekoi8u::ucfirst(@);
sub Ekoi8u::ucfirst_();
sub Ekoi8u::uc(@);
sub Ekoi8u::uc_();
sub Ekoi8u::fc(@);
sub Ekoi8u::fc_();
sub Ekoi8u::ignorecase;
sub Ekoi8u::classic_character_class;
sub Ekoi8u::capture;
sub Ekoi8u::chr(;$);
sub Ekoi8u::chr_();
sub Ekoi8u::glob($);
sub Ekoi8u::glob_();

sub KOI8U::ord(;$);
sub KOI8U::ord_();
sub KOI8U::reverse(@);
sub KOI8U::getc(;*@);
sub KOI8U::length(;$);
sub KOI8U::substr($$;$$);
sub KOI8U::index($$;$);
sub KOI8U::rindex($$;$);
sub KOI8U::escape(;$);

#
# Regexp work
#
use vars qw(
    $re_a
    $re_t
    $re_n
    $re_r
);

#
# Character class
#
use vars qw(
    $dot
    $dot_s
    $eD
    $eS
    $eW
    $eH
    $eV
    $eR
    $eN
    $not_alnum
    $not_alpha
    $not_ascii
    $not_blank
    $not_cntrl
    $not_digit
    $not_graph
    $not_lower
    $not_lower_i
    $not_print
    $not_punct
    $not_space
    $not_upper
    $not_upper_i
    $not_word
    $not_xdigit
    $eb
    $eB
);

${Ekoi8u::dot}         = qr{(?>[^\x0A])};
${Ekoi8u::dot_s}       = qr{(?>[\x00-\xFF])};
${Ekoi8u::eD}          = qr{(?>[^0-9])};

# Vertical tabs are now whitespace
# \s in a regex now matches a vertical tab in all circumstances.
# http://search.cpan.org/dist/perl-5.18.0/pod/perldelta.pod#Vertical_tabs_are_now_whitespace
# ${Ekoi8u::eS}          = qr{(?>[^\x09\x0A    \x0C\x0D\x20])};
# ${Ekoi8u::eS}          = qr{(?>[^\x09\x0A\x0B\x0C\x0D\x20])};
${Ekoi8u::eS}            = qr{(?>[^\s])};

${Ekoi8u::eW}            = qr{(?>[^0-9A-Z_a-z])};
${Ekoi8u::eH}            = qr{(?>[^\x09\x20])};
${Ekoi8u::eV}            = qr{(?>[^\x0A\x0B\x0C\x0D])};
${Ekoi8u::eR}            = qr{(?>\x0D\x0A|[\x0A\x0D])};
${Ekoi8u::eN}            = qr{(?>[^\x0A])};
${Ekoi8u::not_alnum}     = qr{(?>[^\x30-\x39\x41-\x5A\x61-\x7A])};
${Ekoi8u::not_alpha}     = qr{(?>[^\x41-\x5A\x61-\x7A])};
${Ekoi8u::not_ascii}     = qr{(?>[^\x00-\x7F])};
${Ekoi8u::not_blank}     = qr{(?>[^\x09\x20])};
${Ekoi8u::not_cntrl}     = qr{(?>[^\x00-\x1F\x7F])};
${Ekoi8u::not_digit}     = qr{(?>[^\x30-\x39])};
${Ekoi8u::not_graph}     = qr{(?>[^\x21-\x7F])};
${Ekoi8u::not_lower}     = qr{(?>[^\x61-\x7A])};
${Ekoi8u::not_lower_i}   = qr{(?>[^\x41-\x5A\x61-\x7A])}; # Perl 5.16 compatible
# ${Ekoi8u::not_lower_i} = qr{(?>[\x00-\xFF])};                   # older Perl compatible
${Ekoi8u::not_print}     = qr{(?>[^\x20-\x7F])};
${Ekoi8u::not_punct}     = qr{(?>[^\x21-\x2F\x3A-\x3F\x40\x5B-\x5F\x60\x7B-\x7E])};
${Ekoi8u::not_space}     = qr{(?>[^\s\x0B])};
${Ekoi8u::not_upper}     = qr{(?>[^\x41-\x5A])};
${Ekoi8u::not_upper_i}   = qr{(?>[^\x41-\x5A\x61-\x7A])}; # Perl 5.16 compatible
# ${Ekoi8u::not_upper_i} = qr{(?>[\x00-\xFF])};                   # older Perl compatible
${Ekoi8u::not_word}      = qr{(?>[^\x30-\x39\x41-\x5A\x5F\x61-\x7A])};
${Ekoi8u::not_xdigit}    = qr{(?>[^\x30-\x39\x41-\x46\x61-\x66])};
${Ekoi8u::eb}            = qr{(?:\A(?=[0-9A-Z_a-z])|(?<=[\x00-\x2F\x40\x5B-\x5E\x60\x7B-\xFF])(?=[0-9A-Z_a-z])|(?<=[0-9A-Z_a-z])(?=[\x00-\x2F\x40\x5B-\x5E\x60\x7B-\xFF]|\z))};
${Ekoi8u::eB}            = qr{(?:(?<=[0-9A-Z_a-z])(?=[0-9A-Z_a-z])|(?<=[\x00-\x2F\x40\x5B-\x5E\x60\x7B-\xFF])(?=[\x00-\x2F\x40\x5B-\x5E\x60\x7B-\xFF]))};

# avoid: Name "Ekoi8u::foo" used only once: possible typo at here.
${Ekoi8u::dot}         = ${Ekoi8u::dot};
${Ekoi8u::dot_s}       = ${Ekoi8u::dot_s};
${Ekoi8u::eD}          = ${Ekoi8u::eD};
${Ekoi8u::eS}          = ${Ekoi8u::eS};
${Ekoi8u::eW}          = ${Ekoi8u::eW};
${Ekoi8u::eH}          = ${Ekoi8u::eH};
${Ekoi8u::eV}          = ${Ekoi8u::eV};
${Ekoi8u::eR}          = ${Ekoi8u::eR};
${Ekoi8u::eN}          = ${Ekoi8u::eN};
${Ekoi8u::not_alnum}   = ${Ekoi8u::not_alnum};
${Ekoi8u::not_alpha}   = ${Ekoi8u::not_alpha};
${Ekoi8u::not_ascii}   = ${Ekoi8u::not_ascii};
${Ekoi8u::not_blank}   = ${Ekoi8u::not_blank};
${Ekoi8u::not_cntrl}   = ${Ekoi8u::not_cntrl};
${Ekoi8u::not_digit}   = ${Ekoi8u::not_digit};
${Ekoi8u::not_graph}   = ${Ekoi8u::not_graph};
${Ekoi8u::not_lower}   = ${Ekoi8u::not_lower};
${Ekoi8u::not_lower_i} = ${Ekoi8u::not_lower_i};
${Ekoi8u::not_print}   = ${Ekoi8u::not_print};
${Ekoi8u::not_punct}   = ${Ekoi8u::not_punct};
${Ekoi8u::not_space}   = ${Ekoi8u::not_space};
${Ekoi8u::not_upper}   = ${Ekoi8u::not_upper};
${Ekoi8u::not_upper_i} = ${Ekoi8u::not_upper_i};
${Ekoi8u::not_word}    = ${Ekoi8u::not_word};
${Ekoi8u::not_xdigit}  = ${Ekoi8u::not_xdigit};
${Ekoi8u::eb}          = ${Ekoi8u::eb};
${Ekoi8u::eB}          = ${Ekoi8u::eB};

#
# KOI8-U split
#
sub Ekoi8u::split(;$$$) {

    # P.794 29.2.161. split
    # in Chapter 29: Functions
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.951 split
    # in Chapter 27: Functions
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    my $pattern = $_[0];
    my $string  = $_[1];
    my $limit   = $_[2];

    # if $pattern is also omitted or is the literal space, " "
    if (not defined $pattern) {
        $pattern = ' ';
    }

    # if $string is omitted, the function splits the $_ string
    if (not defined $string) {
        if (defined $_) {
            $string = $_;
        }
        else {
            $string = '';
        }
    }

    my @split = ();

    # when string is empty
    if ($string eq '') {

        # resulting list value in list context
        if (wantarray) {
            return @split;
        }

        # count of substrings in scalar context
        else {
            carp "Use of implicit split to \@_ is deprecated" if $^W;
            @_ = @split;
            return scalar @_;
        }
    }

    # split's first argument is more consistently interpreted
    #
    # After some changes earlier in v5.17, split's behavior has been simplified:
    # if the PATTERN argument evaluates to a string containing one space, it is
    # treated the way that a literal string containing one space once was.
    # http://search.cpan.org/dist/perl-5.18.0/pod/perldelta.pod#split's_first_argument_is_more_consistently_interpreted

    # if $pattern is also omitted or is the literal space, " ", the function splits
    # on whitespace, /\s+/, after skipping any leading whitespace
    # (and so on)

    elsif ($pattern eq ' ') {
        if (not defined $limit) {
            return CORE::split(' ', $string);
        }
        else {
            return CORE::split(' ', $string, $limit);
        }
    }

    # if $limit is negative, it is treated as if an arbitrarily large $limit has been specified
    if ((not defined $limit) or ($limit <= 0)) {

        # a pattern capable of matching either the null string or something longer than the
        # null string will split the value of $string into separate characters wherever it
        # matches the null string between characters
        # (and so on)

        if ('' =~ / \A $pattern \z /xms) {
            my $last_subexpression_offsets = _last_subexpression_offsets($pattern);
            my $limit = scalar(() = $string =~ /($pattern)/oxmsg);

            # P.1024 Appendix W.10 Multibyte Processing
            # of ISBN 1-56592-224-7 CJKV Information Processing
            # (and so on)

            # the //m modifier is assumed when you split on the pattern /^/
            # (and so on)

            eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
            #                                                     V
            while ((--$limit > 0) and ($string =~ s/\A((?:$q_char)+?)$pattern//m)) {

                # if the $pattern contains parentheses, then the substring matched by each pair of parentheses
                # is included in the resulting list, interspersed with the fields that are ordinarily returned
                # (and so on)

                local $@;
                eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
                for (my $digit=1; $digit <= ($last_subexpression_offsets + 1); $digit++) {
                    push @split, CORE::eval('$' . $digit);
                }
            }
        }

        else {
            my $last_subexpression_offsets = _last_subexpression_offsets($pattern);

            eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
            #                                 V
            while ($string =~ s/\A((?:$q_char)*?)$pattern//m) {
                local $@;
                eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
                for (my $digit=1; $digit <= ($last_subexpression_offsets + 1); $digit++) {
                    push @split, CORE::eval('$' . $digit);
                }
            }
        }
    }

    elsif ($limit > 0) {
        if ('' =~ / \A $pattern \z /xms) {
            my $last_subexpression_offsets = _last_subexpression_offsets($pattern);
            while ((--$limit > 0) and (CORE::length($string) > 0)) {

                eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
                #                              V
                if ($string =~ s/\A((?:$q_char)+?)$pattern//m) {
                    local $@;
                    for (my $digit=1; $digit <= ($last_subexpression_offsets + 1); $digit++) {
                        push @split, CORE::eval('$' . $digit);
                    }
                }
            }
        }
        else {
            my $last_subexpression_offsets = _last_subexpression_offsets($pattern);
            while ((--$limit > 0) and (CORE::length($string) > 0)) {

                eval q{ no warnings }; # avoid: Complex regular subexpression recursion limit (32766) exceeded at ...
                #                              V
                if ($string =~ s/\A((?:$q_char)*?)$pattern//m) {
                    local $@;
                    for (my $digit=1; $digit <= ($last_subexpression_offsets + 1); $digit++) {
                        push @split, CORE::eval('$' . $digit);
                    }
                }
            }
        }
    }

    if (CORE::length($string) > 0) {
        push @split, $string;
    }

    # if $_[2] (NOT "$limit") is omitted or zero, trailing null fields are stripped from the result
    if ((not defined $_[2]) or ($_[2] == 0)) {
        while ((scalar(@split) >= 1) and ($split[-1] eq '')) {
            pop @split;
        }
    }

    # resulting list value in list context
    if (wantarray) {
        return @split;
    }

    # count of substrings in scalar context
    else {
        carp "Use of implicit split to \@_ is deprecated" if $^W;
        @_ = @split;
        return scalar @_;
    }
}

#
# get last subexpression offsets
#
sub _last_subexpression_offsets {
    my $pattern = $_[0];

    # remove comment
    $pattern =~ s/\(\?\# .*? \)//oxmsg;

    my $modifier = '';
    if ($pattern =~ /\(\?\^? ([\-A-Za-z]+) :/oxms) {
        $modifier = $1;
        $modifier =~ s/-[A-Za-z]*//;
    }

    # with /x modifier
    my @char = ();
    if ($modifier =~ /x/oxms) {
        @char = $pattern =~ /\G((?>
            [^\\\#\[\(] |
            \\ $q_char      |
            \# (?>[^\n]*) $ |
            \[ (?>(?:[^\\\]]|\\\\|\\\]|$q_char)+) \] |
            \(\?            |
                $q_char
        ))/oxmsg;
    }

    # without /x modifier
    else {
        @char = $pattern =~ /\G((?>
            [^\\\[\(] |
            \\ $q_char      |
            \[ (?>(?:[^\\\]]|\\\\|\\\]|$q_char)+) \] |
            \(\?            |
                $q_char
        ))/oxmsg;
    }

    return scalar grep { $_ eq '(' } @char;
}

#
# KOI8-U transliteration (tr///)
#
sub Ekoi8u::tr($$$$;$) {

    my $bind_operator   = $_[1];
    my $searchlist      = $_[2];
    my $replacementlist = $_[3];
    my $modifier        = $_[4] || '';

    if ($modifier =~ /r/oxms) {
        if ($bind_operator =~ / !~ /oxms) {
            croak "Using !~ with tr///r doesn't make sense";
        }
    }

    my @char            = $_[0] =~ /\G (?>$q_char) /oxmsg;
    my @searchlist      = _charlist_tr($searchlist);
    my @replacementlist = _charlist_tr($replacementlist);

    my %tr = ();
    for (my $i=0; $i <= $#searchlist; $i++) {
        if (not exists $tr{$searchlist[$i]}) {
            if (defined $replacementlist[$i] and ($replacementlist[$i] ne '')) {
                $tr{$searchlist[$i]} = $replacementlist[$i];
            }
            elsif ($modifier =~ /d/oxms) {
                $tr{$searchlist[$i]} = '';
            }
            elsif (defined $replacementlist[-1] and ($replacementlist[-1] ne '')) {
                $tr{$searchlist[$i]} = $replacementlist[-1];
            }
            else {
                $tr{$searchlist[$i]} = $searchlist[$i];
            }
        }
    }

    my $tr = 0;
    my $replaced = '';
    if ($modifier =~ /c/oxms) {
        while (defined(my $char = shift @char)) {
            if (not exists $tr{$char}) {
                if (defined $replacementlist[-1]) {
                    $replaced .= $replacementlist[-1];
                }
                $tr++;
                if ($modifier =~ /s/oxms) {
                    while (@char and (not exists $tr{$char[0]})) {
                        shift @char;
                        $tr++;
                    }
                }
            }
            else {
                $replaced .= $char;
            }
        }
    }
    else {
        while (defined(my $char = shift @char)) {
            if (exists $tr{$char}) {
                $replaced .= $tr{$char};
                $tr++;
                if ($modifier =~ /s/oxms) {
                    while (@char and (exists $tr{$char[0]}) and ($tr{$char[0]} eq $tr{$char})) {
                        shift @char;
                        $tr++;
                    }
                }
            }
            else {
                $replaced .= $char;
            }
        }
    }

    if ($modifier =~ /r/oxms) {
        return $replaced;
    }
    else {
        $_[0] = $replaced;
        if ($bind_operator =~ / !~ /oxms) {
            return not $tr;
        }
        else {
            return $tr;
        }
    }
}

#
# KOI8-U chop
#
sub Ekoi8u::chop(@) {

    my $chop;
    if (@_ == 0) {
        my @char = /\G (?>$q_char) /oxmsg;
        $chop = pop @char;
        $_ = join '', @char;
    }
    else {
        for (@_) {
            my @char = /\G (?>$q_char) /oxmsg;
            $chop = pop @char;
            $_ = join '', @char;
        }
    }
    return $chop;
}

#
# KOI8-U index by octet
#
sub Ekoi8u::index($$;$) {

    my($str,$substr,$position) = @_;
    $position ||= 0;
    my $pos = 0;

    while ($pos < CORE::length($str)) {
        if (CORE::substr($str,$pos,CORE::length($substr)) eq $substr) {
            if ($pos >= $position) {
                return $pos;
            }
        }
        if (CORE::substr($str,$pos) =~ /\A ($q_char) /oxms) {
            $pos += CORE::length($1);
        }
        else {
            $pos += 1;
        }
    }
    return -1;
}

#
# KOI8-U reverse index
#
sub Ekoi8u::rindex($$;$) {

    my($str,$substr,$position) = @_;
    $position ||= CORE::length($str) - 1;
    my $pos = 0;
    my $rindex = -1;

    while (($pos < CORE::length($str)) and ($pos <= $position)) {
        if (CORE::substr($str,$pos,CORE::length($substr)) eq $substr) {
            $rindex = $pos;
        }
        if (CORE::substr($str,$pos) =~ /\A ($q_char) /oxms) {
            $pos += CORE::length($1);
        }
        else {
            $pos += 1;
        }
    }
    return $rindex;
}

#
# KOI8-U lower case first with parameter
#
sub Ekoi8u::lcfirst(@) {
    if (@_) {
        my $s = shift @_;
        if (@_ and wantarray) {
            return Ekoi8u::lc(CORE::substr($s,0,1)) . CORE::substr($s,1), @_;
        }
        else {
            return Ekoi8u::lc(CORE::substr($s,0,1)) . CORE::substr($s,1);
        }
    }
    else {
        return Ekoi8u::lc(CORE::substr($_,0,1)) . CORE::substr($_,1);
    }
}

#
# KOI8-U lower case first without parameter
#
sub Ekoi8u::lcfirst_() {
    return Ekoi8u::lc(CORE::substr($_,0,1)) . CORE::substr($_,1);
}

#
# KOI8-U lower case with parameter
#
sub Ekoi8u::lc(@) {
    if (@_) {
        my $s = shift @_;
        if (@_ and wantarray) {
            return join('', map {defined($lc{$_}) ? $lc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg)), @_;
        }
        else {
            return join('', map {defined($lc{$_}) ? $lc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg));
        }
    }
    else {
        return Ekoi8u::lc_();
    }
}

#
# KOI8-U lower case without parameter
#
sub Ekoi8u::lc_() {
    my $s = $_;
    return join '', map {defined($lc{$_}) ? $lc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg);
}

#
# KOI8-U upper case first with parameter
#
sub Ekoi8u::ucfirst(@) {
    if (@_) {
        my $s = shift @_;
        if (@_ and wantarray) {
            return Ekoi8u::uc(CORE::substr($s,0,1)) . CORE::substr($s,1), @_;
        }
        else {
            return Ekoi8u::uc(CORE::substr($s,0,1)) . CORE::substr($s,1);
        }
    }
    else {
        return Ekoi8u::uc(CORE::substr($_,0,1)) . CORE::substr($_,1);
    }
}

#
# KOI8-U upper case first without parameter
#
sub Ekoi8u::ucfirst_() {
    return Ekoi8u::uc(CORE::substr($_,0,1)) . CORE::substr($_,1);
}

#
# KOI8-U upper case with parameter
#
sub Ekoi8u::uc(@) {
    if (@_) {
        my $s = shift @_;
        if (@_ and wantarray) {
            return join('', map {defined($uc{$_}) ? $uc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg)), @_;
        }
        else {
            return join('', map {defined($uc{$_}) ? $uc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg));
        }
    }
    else {
        return Ekoi8u::uc_();
    }
}

#
# KOI8-U upper case without parameter
#
sub Ekoi8u::uc_() {
    my $s = $_;
    return join '', map {defined($uc{$_}) ? $uc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg);
}

#
# KOI8-U fold case with parameter
#
sub Ekoi8u::fc(@) {
    if (@_) {
        my $s = shift @_;
        if (@_ and wantarray) {
            return join('', map {defined($fc{$_}) ? $fc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg)), @_;
        }
        else {
            return join('', map {defined($fc{$_}) ? $fc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg));
        }
    }
    else {
        return Ekoi8u::fc_();
    }
}

#
# KOI8-U fold case without parameter
#
sub Ekoi8u::fc_() {
    my $s = $_;
    return join '', map {defined($fc{$_}) ? $fc{$_} : $_} ($s =~ /\G ($q_char) /oxmsg);
}

#
# KOI8-U regexp capture
#
{
    sub Ekoi8u::capture {
        return $_[0];
    }
}

#
# KOI8-U regexp ignore case modifier
#
sub Ekoi8u::ignorecase {

    my @string = @_;
    my $metachar = qr/[\@\\|[\]{]/oxms;

    # ignore case of $scalar or @array
    for my $string (@string) {

        # split regexp
        my @char = $string =~ /\G (?>\[\^|\\$q_char|$q_char) /oxmsg;

        # unescape character
        for (my $i=0; $i <= $#char; $i++) {
            next if not defined $char[$i];

            # open character class [...]
            if ($char[$i] eq '[') {
                my $left = $i;

                # [] make die "unmatched [] in regexp ...\n"

                if ($char[$i+1] eq ']') {
                    $i++;
                }

                while (1) {
                    if (++$i > $#char) {
                        croak "Unmatched [] in regexp";
                    }
                    if ($char[$i] eq ']') {
                        my $right = $i;
                        my @charlist = charlist_qr(@char[$left+1..$right-1], 'i');

                        # escape character
                        for my $char (@charlist) {
                            if (0) {
                            }

                            elsif ($char =~ /\A [.|)] \z/oxms) {
                                $char = '\\' . $char;
                            }
                        }

                        # [...]
                        splice @char, $left, $right-$left+1, '(?:' . join('|', @charlist) . ')';

                        $i = $left;
                        last;
                    }
                }
            }

            # open character class [^...]
            elsif ($char[$i] eq '[^') {
                my $left = $i;

                # [^] make die "unmatched [] in regexp ...\n"

                if ($char[$i+1] eq ']') {
                    $i++;
                }

                while (1) {
                    if (++$i > $#char) {
                        croak "Unmatched [] in regexp";
                    }
                    if ($char[$i] eq ']') {
                        my $right = $i;
                        my @charlist = charlist_not_qr(@char[$left+1..$right-1], 'i');

                        # escape character
                        for my $char (@charlist) {
                            if (0) {
                            }

                            elsif ($char =~ /\A [.|)] \z/oxms) {
                                $char = '\\' . $char;
                            }
                        }

                        # [^...]
                        splice @char, $left, $right-$left+1, '(?!' . join('|', @charlist) . ")(?:$your_char)";

                        $i = $left;
                        last;
                    }
                }
            }

            # rewrite classic character class or escape character
            elsif (my $char = classic_character_class($char[$i])) {
                $char[$i] = $char;
            }

            # with /i modifier
            elsif ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) {
                my $uc = Ekoi8u::uc($char[$i]);
                my $fc = Ekoi8u::fc($char[$i]);
                if ($uc ne $fc) {
                    if (CORE::length($fc) == 1) {
                        $char[$i] = '['   . $uc       . $fc . ']';
                    }
                    else {
                        $char[$i] = '(?:' . $uc . '|' . $fc . ')';
                    }
                }
            }
        }

        # characterize
        for (my $i=0; $i <= $#char; $i++) {
            next if not defined $char[$i];

            if (0) {
            }

            # quote character before ? + * {
            elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
                if ($char[$i-1] !~ /\A [\x00-\xFF] \z/oxms) {
                    $char[$i-1] = '(?:' . $char[$i-1] . ')';
                }
            }
        }

        $string = join '', @char;
    }

    # make regexp string
    return @string;
}

#
# classic character class ( \D \S \W \d \s \w \C \X \H \V \h \v \R \N \b \B )
#
sub Ekoi8u::classic_character_class {
    my($char) = @_;

    return {
        '\D' => '${Ekoi8u::eD}',
        '\S' => '${Ekoi8u::eS}',
        '\W' => '${Ekoi8u::eW}',
        '\d' => '[0-9]',

        # Before Perl 5.6, \s only matched the five whitespace characters
        # tab, newline, form-feed, carriage return, and the space character
        # itself, which, taken together, is the character class [\t\n\f\r ].

        # Vertical tabs are now whitespace
        # \s in a regex now matches a vertical tab in all circumstances.
        # http://search.cpan.org/dist/perl-5.18.0/pod/perldelta.pod#Vertical_tabs_are_now_whitespace
        #            \t  \n  \v  \f  \r space
        # '\s' => '[\x09\x0A    \x0C\x0D\x20]',
        # '\s' => '[\x09\x0A\x0B\x0C\x0D\x20]',
        '\s'   => '\s',

        '\w' => '[0-9A-Z_a-z]',
        '\C' => '[\x00-\xFF]',
        '\X' => 'X',

        # \h \v \H \V

        # P.114 Character Class Shortcuts
        # in Chapter 7: In the World of Regular Expressions
        # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

        # P.357 13.2.3 Whitespace
        # in Chapter 13: perlrecharclass: Perl Regular Expression Character Classes
        # of ISBN-13: 978-1-906966-02-7 The Perl Language Reference Manual (for Perl version 5.12.1)
        #
        # 0x00009   CHARACTER TABULATION  h s
        # 0x0000a         LINE FEED (LF)   vs
        # 0x0000b        LINE TABULATION   v
        # 0x0000c         FORM FEED (FF)   vs
        # 0x0000d   CARRIAGE RETURN (CR)   vs
        # 0x00020                  SPACE  h s

        # P.196 Table 5-9. Alphanumeric regex metasymbols
        # in Chapter 5. Pattern Matching
        # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

        # (and so on)

        '\H' => '${Ekoi8u::eH}',
        '\V' => '${Ekoi8u::eV}',
        '\h' => '[\x09\x20]',
        '\v' => '[\x0A\x0B\x0C\x0D]',
        '\R' => '${Ekoi8u::eR}',

        # \N
        #
        # http://perldoc.perl.org/perlre.html
        # Character Classes and other Special Escapes
        # Any character but \n (experimental). Not affected by /s modifier

        '\N' => '${Ekoi8u::eN}',

        # \b \B

        # P.180 Boundaries: The \b and \B Assertions
        # in Chapter 5: Pattern Matching
        # of ISBN 0-596-00027-8 Programming Perl Third Edition.

        # P.219 Boundaries: The \b and \B Assertions
        # in Chapter 5: Pattern Matching
        # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

        # \b really means (?:(?<=\w)(?!\w)|(?
        #           or (?:(?<=\A|\W)(?=\w)|(?<=\w)(?=\W|\z))
        '\b' => '${Ekoi8u::eb}',

        # \B really means (?:(?<=\w)(?=\w)|(?
        #              or (?:(?<=\w)(?=\w)|(?<=\W)(?=\W))
        '\B' => '${Ekoi8u::eB}',

    }->{$char} || '';
}

#
# prepare KOI8-U characters per length
#

# 1 octet characters
my @chars1 = ();
sub chars1 {
    if (@chars1) {
        return @chars1;
    }
    if (exists $range_tr{1}) {
        my @ranges = @{ $range_tr{1} };
        while (my @range = splice(@ranges,0,1)) {
            for my $oct0 (@{$range[0]}) {
                push @chars1, pack 'C', $oct0;
            }
        }
    }
    return @chars1;
}

# 2 octets characters
my @chars2 = ();
sub chars2 {
    if (@chars2) {
        return @chars2;
    }
    if (exists $range_tr{2}) {
        my @ranges = @{ $range_tr{2} };
        while (my @range = splice(@ranges,0,2)) {
            for my $oct0 (@{$range[0]}) {
                for my $oct1 (@{$range[1]}) {
                    push @chars2, pack 'CC', $oct0,$oct1;
                }
            }
        }
    }
    return @chars2;
}

# 3 octets characters
my @chars3 = ();
sub chars3 {
    if (@chars3) {
        return @chars3;
    }
    if (exists $range_tr{3}) {
        my @ranges = @{ $range_tr{3} };
        while (my @range = splice(@ranges,0,3)) {
            for my $oct0 (@{$range[0]}) {
                for my $oct1 (@{$range[1]}) {
                    for my $oct2 (@{$range[2]}) {
                        push @chars3, pack 'CCC', $oct0,$oct1,$oct2;
                    }
                }
            }
        }
    }
    return @chars3;
}

# 4 octets characters
my @chars4 = ();
sub chars4 {
    if (@chars4) {
        return @chars4;
    }
    if (exists $range_tr{4}) {
        my @ranges = @{ $range_tr{4} };
        while (my @range = splice(@ranges,0,4)) {
            for my $oct0 (@{$range[0]}) {
                for my $oct1 (@{$range[1]}) {
                    for my $oct2 (@{$range[2]}) {
                        for my $oct3 (@{$range[3]}) {
                            push @chars4, pack 'CCCC', $oct0,$oct1,$oct2,$oct3;
                        }
                    }
                }
            }
        }
    }
    return @chars4;
}

#
# KOI8-U open character list for tr
#
sub _charlist_tr {

    local $_ = shift @_;

    # unescape character
    my @char = ();
    while (not /\G \z/oxmsgc) {
        if (/\G (\\0?55|\\x2[Dd]|\\-) /oxmsgc) {
            push @char, '\-';
        }
        elsif (/\G \\ ([0-7]{2,3}) /oxmsgc) {
            push @char, CORE::chr(oct $1);
        }
        elsif (/\G \\x ([0-9A-Fa-f]{1,2}) /oxmsgc) {
            push @char, CORE::chr(hex $1);
        }
        elsif (/\G \\c ([\x40-\x5F]) /oxmsgc) {
            push @char, CORE::chr(CORE::ord($1) & 0x1F);
        }
        elsif (/\G (\\ [0nrtfbae]) /oxmsgc) {
            push @char, {
                '\0' => "\0",
                '\n' => "\n",
                '\r' => "\r",
                '\t' => "\t",
                '\f' => "\f",
                '\b' => "\x08", # \b means backspace in character class
                '\a' => "\a",
                '\e' => "\e",
            }->{$1};
        }
        elsif (/\G \\ ($q_char) /oxmsgc) {
            push @char, $1;
        }
        elsif (/\G ($q_char) /oxmsgc) {
            push @char, $1;
        }
    }

    # join separated multiple-octet
    @char = join('',@char) =~ /\G (?>\\-|$q_char) /oxmsg;

    # unescape '-'
    my @i = ();
    for my $i (0 .. $#char) {
        if ($char[$i] eq '\-') {
            $char[$i] = '-';
        }
        elsif ($char[$i] eq '-') {
            if ((0 < $i) and ($i < $#char)) {
                push @i, $i;
            }
        }
    }

    # open character list (reverse for splice)
    for my $i (CORE::reverse @i) {
        my @range = ();

        # range error
        if ((CORE::length($char[$i-1]) > CORE::length($char[$i+1])) or ($char[$i-1] gt $char[$i+1])) {
            croak "Invalid tr/// range \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
        }

        # range of multiple-octet code
        if (CORE::length($char[$i-1]) == 1) {
            if (CORE::length($char[$i+1]) == 1) {
                push @range, grep {($char[$i-1] le $_) and ($_ le $char[$i+1])} chars1();
            }
            elsif (CORE::length($char[$i+1]) == 2) {
                push @range, grep {$char[$i-1] le $_}                           chars1();
                push @range, grep {$_ le $char[$i+1]}                           chars2();
            }
            elsif (CORE::length($char[$i+1]) == 3) {
                push @range, grep {$char[$i-1] le $_}                           chars1();
                push @range,                                                    chars2();
                push @range, grep {$_ le $char[$i+1]}                           chars3();
            }
            elsif (CORE::length($char[$i+1]) == 4) {
                push @range, grep {$char[$i-1] le $_}                           chars1();
                push @range,                                                    chars2();
                push @range,                                                    chars3();
                push @range, grep {$_ le $char[$i+1]}                           chars4();
            }
            else {
                croak "Invalid tr/// range (over 4octets) \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
            }
        }
        elsif (CORE::length($char[$i-1]) == 2) {
            if (CORE::length($char[$i+1]) == 2) {
                push @range, grep {($char[$i-1] le $_) and ($_ le $char[$i+1])} chars2();
            }
            elsif (CORE::length($char[$i+1]) == 3) {
                push @range, grep {$char[$i-1] le $_}                           chars2();
                push @range, grep {$_ le $char[$i+1]}                           chars3();
            }
            elsif (CORE::length($char[$i+1]) == 4) {
                push @range, grep {$char[$i-1] le $_}                           chars2();
                push @range,                                                    chars3();
                push @range, grep {$_ le $char[$i+1]}                           chars4();
            }
            else {
                croak "Invalid tr/// range (over 4octets) \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
            }
        }
        elsif (CORE::length($char[$i-1]) == 3) {
            if (CORE::length($char[$i+1]) == 3) {
                push @range, grep {($char[$i-1] le $_) and ($_ le $char[$i+1])} chars3();
            }
            elsif (CORE::length($char[$i+1]) == 4) {
                push @range, grep {$char[$i-1] le $_}                           chars3();
                push @range, grep {$_ le $char[$i+1]}                           chars4();
            }
            else {
                croak "Invalid tr/// range (over 4octets) \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
            }
        }
        elsif (CORE::length($char[$i-1]) == 4) {
            if (CORE::length($char[$i+1]) == 4) {
                push @range, grep {($char[$i-1] le $_) and ($_ le $char[$i+1])} chars4();
            }
            else {
                croak "Invalid tr/// range (over 4octets) \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
            }
        }
        else {
            croak "Invalid tr/// range (over 4octets) \"\\x" . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]) . '"';
        }

        splice @char, $i-1, 3, @range;
    }

    return @char;
}

#
# KOI8-U open character class
#
sub _cc {
    if (scalar(@_) == 0) {
        die __FILE__, ": subroutine cc got no parameter.\n";
    }
    elsif (scalar(@_) == 1) {
        return sprintf('\x%02X',$_[0]);
    }
    elsif (scalar(@_) == 2) {
        if ($_[0] > $_[1]) {
            die __FILE__, ": subroutine cc got \$_[0] > \$_[1] parameters).\n";
        }
        elsif ($_[0] == $_[1]) {
            return sprintf('\x%02X',$_[0]);
        }
        elsif (($_[0]+1) == $_[1]) {
            return sprintf('[\\x%02X\\x%02X]',$_[0],$_[1]);
        }
        else {
            return sprintf('[\\x%02X-\\x%02X]',$_[0],$_[1]);
        }
    }
    else {
        die __FILE__, ": subroutine cc got 3 or more parameters (@{[scalar(@_)]} parameters).\n";
    }
}

#
# KOI8-U octet range
#
sub _octets {
    my $length = shift @_;

    if ($length == 1) {
        my($a1) = unpack 'C', $_[0];
        my($z1) = unpack 'C', $_[1];

        if ($a1 > $z1) {
            croak 'Invalid [] range in regexp (CORE::ord(A) > CORE::ord(B)) ' . '\x' . unpack('H*',$a1) . '-\x' . unpack('H*',$z1);
        }

        if ($a1 == $z1) {
            return sprintf('\x%02X',$a1);
        }
        elsif (($a1+1) == $z1) {
            return sprintf('\x%02X\x%02X',$a1,$z1);
        }
        else {
            return sprintf('\x%02X-\x%02X',$a1,$z1);
        }
    }
    else {
        die __FILE__, ": subroutine _octets got invalid length ($length).\n";
    }
}

#
# KOI8-U range regexp
#
sub _range_regexp {
    my($length,$first,$last) = @_;

    my @range_regexp = ();
    if (not exists $range_tr{$length}) {
        return @range_regexp;
    }

    my @ranges = @{ $range_tr{$length} };
    while (my @range = splice(@ranges,0,$length)) {
        my $min = '';
        my $max = '';
        for (my $i=0; $i < $length; $i++) {
            $min .= pack 'C', $range[$i][0];
            $max .= pack 'C', $range[$i][-1];
        }

# min___max
#            FIRST_____________LAST
#       (nothing)

        if ($max lt $first) {
        }

#            **********
#       min_________max
#            FIRST_____________LAST
#            **********

        elsif (($min le $first) and ($first le $max) and ($max le $last)) {
            push @range_regexp, _octets($length,$first,$max,$min,$max);
        }

#            **********************
#            min________________max
#            FIRST_____________LAST
#            **********************

        elsif (($min eq $first) and ($max eq $last)) {
            push @range_regexp, _octets($length,$first,$last,$min,$max);
        }

#                   *********
#                   min___max
#            FIRST_____________LAST
#                   *********

        elsif (($first le $min) and ($max le $last)) {
            push @range_regexp, _octets($length,$min,$max,$min,$max);
        }

#            **********************
#       min__________________________max
#            FIRST_____________LAST
#            **********************

        elsif (($min le $first) and ($last le $max)) {
            push @range_regexp, _octets($length,$first,$last,$min,$max);
        }

#                         *********
#                         min________max
#            FIRST_____________LAST
#                         *********

        elsif (($first le $min) and ($min le $last) and ($last le $max)) {
            push @range_regexp, _octets($length,$min,$last,$min,$max);
        }

#                                    min___max
#            FIRST_____________LAST
#                              (nothing)

        elsif ($last lt $min) {
        }

        else {
            die __FILE__, ": subroutine _range_regexp panic.\n";
        }
    }

    return @range_regexp;
}

#
# KOI8-U open character list for qr and not qr
#
sub _charlist {

    my $modifier = pop @_;
    my @char = @_;

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {

        # escape - to ...
        if ($char[$i] eq '-') {
            if ((0 < $i) and ($i < $#char)) {
                $char[$i] = '...';
            }
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = hexchr($1);
        }

        # \b{...}      --> b\{...}
        # \B{...}      --> B\{...}
        # \N{CHARNAME} --> N\{CHARNAME}
        # \p{PROPERTY} --> p\{PROPERTY}
        # \P{PROPERTY} --> P\{PROPERTY}
        elsif ($char[$i] =~ /\A \\ ([bBNpP]) ( \{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1 . '\\' . $2;
        }

        # \p, \P, \X --> p, P, X
        elsif ($char[$i] =~ /\A \\ ( [pPX] ) \z/oxms) {
            $char[$i] = $1;
        }

        elsif ($char[$i] =~ /\A \\ ([0-7]{2,3}) \z/oxms) {
            $char[$i] = CORE::chr oct $1;
        }
        elsif ($char[$i] =~ /\A \\x ([0-9A-Fa-f]{1,2}) \z/oxms) {
            $char[$i] = CORE::chr hex $1;
        }
        elsif ($char[$i] =~ /\A \\c ([\x40-\x5F]) \z/oxms) {
            $char[$i] = CORE::chr(CORE::ord($1) & 0x1F);
        }
        elsif ($char[$i] =~ /\A (\\ [0nrtfbaedswDSWHVhvR]) \z/oxms) {
            $char[$i] = {
                '\0' => "\0",
                '\n' => "\n",
                '\r' => "\r",
                '\t' => "\t",
                '\f' => "\f",
                '\b' => "\x08", # \b means backspace in character class
                '\a' => "\a",
                '\e' => "\e",
                '\d' => '[0-9]',

                # Vertical tabs are now whitespace
                # \s in a regex now matches a vertical tab in all circumstances.
                # http://search.cpan.org/dist/perl-5.18.0/pod/perldelta.pod#Vertical_tabs_are_now_whitespace
                #            \t  \n  \v  \f  \r space
                # '\s' => '[\x09\x0A    \x0C\x0D\x20]',
                # '\s' => '[\x09\x0A\x0B\x0C\x0D\x20]',
                '\s'   => '\s',

                '\w' => '[0-9A-Z_a-z]',
                '\D' => '${Ekoi8u::eD}',
                '\S' => '${Ekoi8u::eS}',
                '\W' => '${Ekoi8u::eW}',

                '\H' => '${Ekoi8u::eH}',
                '\V' => '${Ekoi8u::eV}',
                '\h' => '[\x09\x20]',
                '\v' => '[\x0A\x0B\x0C\x0D]',
                '\R' => '${Ekoi8u::eR}',

            }->{$1};
        }

        # POSIX-style character classes
        elsif ($ignorecase and ($char[$i] =~ /\A ( \[\: \^? (?:lower|upper) :\] ) \z/oxms)) {
            $char[$i] = {

                '[:lower:]'   => '[\x41-\x5A\x61-\x7A]',
                '[:upper:]'   => '[\x41-\x5A\x61-\x7A]',
                '[:^lower:]'  => '${Ekoi8u::not_lower_i}',
                '[:^upper:]'  => '${Ekoi8u::not_upper_i}',

            }->{$1};
        }
        elsif ($char[$i] =~ /\A ( \[\: \^? (?:alnum|alpha|ascii|blank|cntrl|digit|graph|lower|print|punct|space|upper|word|xdigit) :\] ) \z/oxms) {
            $char[$i] = {

                '[:alnum:]'   => '[\x30-\x39\x41-\x5A\x61-\x7A]',
                '[:alpha:]'   => '[\x41-\x5A\x61-\x7A]',
                '[:ascii:]'   => '[\x00-\x7F]',
                '[:blank:]'   => '[\x09\x20]',
                '[:cntrl:]'   => '[\x00-\x1F\x7F]',
                '[:digit:]'   => '[\x30-\x39]',
                '[:graph:]'   => '[\x21-\x7F]',
                '[:lower:]'   => '[\x61-\x7A]',
                '[:print:]'   => '[\x20-\x7F]',
                '[:punct:]'   => '[\x21-\x2F\x3A-\x3F\x40\x5B-\x5F\x60\x7B-\x7E]',

                # P.174 POSIX-Style Character Classes
                # in Chapter 5: Pattern Matching
                # of ISBN 0-596-00027-8 Programming Perl Third Edition.

                # P.311 11.2.4 Character Classes and other Special Escapes
                # in Chapter 11: perlre: Perl regular expressions
                # of ISBN-13: 978-1-906966-02-7 The Perl Language Reference Manual (for Perl version 5.12.1)

                # P.210 POSIX-Style Character Classes
                # in Chapter 5: Pattern Matching
                # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

                '[:space:]'   => '[\s\x0B]', # "\s" plus vertical tab ("\cK")

                '[:upper:]'   => '[\x41-\x5A]',
                '[:word:]'    => '[\x30-\x39\x41-\x5A\x5F\x61-\x7A]',
                '[:xdigit:]'  => '[\x30-\x39\x41-\x46\x61-\x66]',
                '[:^alnum:]'  => '${Ekoi8u::not_alnum}',
                '[:^alpha:]'  => '${Ekoi8u::not_alpha}',
                '[:^ascii:]'  => '${Ekoi8u::not_ascii}',
                '[:^blank:]'  => '${Ekoi8u::not_blank}',
                '[:^cntrl:]'  => '${Ekoi8u::not_cntrl}',
                '[:^digit:]'  => '${Ekoi8u::not_digit}',
                '[:^graph:]'  => '${Ekoi8u::not_graph}',
                '[:^lower:]'  => '${Ekoi8u::not_lower}',
                '[:^print:]'  => '${Ekoi8u::not_print}',
                '[:^punct:]'  => '${Ekoi8u::not_punct}',
                '[:^space:]'  => '${Ekoi8u::not_space}',
                '[:^upper:]'  => '${Ekoi8u::not_upper}',
                '[:^word:]'   => '${Ekoi8u::not_word}',
                '[:^xdigit:]' => '${Ekoi8u::not_xdigit}',

            }->{$1};
        }
        elsif ($char[$i] =~ /\A \\ ($q_char) \z/oxms) {
            $char[$i] = $1;
        }
    }

    # open character list
    my @singleoctet   = ();
    my @multipleoctet = ();
    for (my $i=0; $i <= $#char; ) {

        # escaped -
        if (defined($char[$i+1]) and ($char[$i+1] eq '...')) {
            $i += 1;
            next;
        }

        # make range regexp
        elsif ($char[$i] eq '...') {

            # range error
            if (CORE::length($char[$i-1]) > CORE::length($char[$i+1])) {
                croak 'Invalid [] range in regexp (length(A) > length(B)) ' . '\x' . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]);
            }
            elsif (CORE::length($char[$i-1]) == CORE::length($char[$i+1])) {
                if ($char[$i-1] gt $char[$i+1]) {
                    croak 'Invalid [] range in regexp (CORE::ord(A) > CORE::ord(B)) ' . '\x' . unpack('H*',$char[$i-1]) . '-\x' . unpack('H*',$char[$i+1]);
                }
            }

            # make range regexp per length
            for my $length (CORE::length($char[$i-1]) .. CORE::length($char[$i+1])) {
                my @regexp = ();

                # is first and last
                if (($length == CORE::length($char[$i-1])) and ($length == CORE::length($char[$i+1]))) {
                    push @regexp, _range_regexp($length, $char[$i-1], $char[$i+1]);
                }

                # is first
                elsif ($length == CORE::length($char[$i-1])) {
                    push @regexp, _range_regexp($length, $char[$i-1], "\xFF" x $length);
                }

                # is inside in first and last
                elsif ((CORE::length($char[$i-1]) < $length) and ($length < CORE::length($char[$i+1]))) {
                    push @regexp, _range_regexp($length, "\x00" x $length, "\xFF" x $length);
                }

                # is last
                elsif ($length == CORE::length($char[$i+1])) {
                    push @regexp, _range_regexp($length, "\x00" x $length, $char[$i+1]);
                }

                else {
                    die __FILE__, ": subroutine make_regexp panic.\n";
                }

                if ($length == 1) {
                    push @singleoctet, @regexp;
                }
                else {
                    push @multipleoctet, @regexp;
                }
            }

            $i += 2;
        }

        # with /i modifier
        elsif ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) {
            if ($modifier =~ /i/oxms) {
                my $uc = Ekoi8u::uc($char[$i]);
                my $fc = Ekoi8u::fc($char[$i]);
                if ($uc ne $fc) {
                    if (CORE::length($fc) == 1) {
                        push @singleoctet, $uc, $fc;
                    }
                    else {
                        push @singleoctet,   $uc;
                        push @multipleoctet, $fc;
                    }
                }
                else {
                    push @singleoctet, $char[$i];
                }
            }
            else {
                push @singleoctet, $char[$i];
            }
            $i += 1;
        }

        # single character of single octet code
        elsif ($char[$i] =~ /\A (?: \\h ) \z/oxms) {
            push @singleoctet, "\t", "\x20";
            $i += 1;
        }
        elsif ($char[$i] =~ /\A (?: \\v ) \z/oxms) {
            push @singleoctet, "\x0A", "\x0B", "\x0C", "\x0D";
            $i += 1;
        }
        elsif ($char[$i] =~ /\A (?: \\d | \\s | \\w ) \z/oxms) {
            push @singleoctet, $char[$i];
            $i += 1;
        }

        # single character of multiple-octet code
        else {
            push @multipleoctet, $char[$i];
            $i += 1;
        }
    }

    # quote metachar
    for (@singleoctet) {
        if ($_ eq '...') {
            $_ = '-';
        }
        elsif (/\A \n \z/oxms) {
            $_ = '\n';
        }
        elsif (/\A \r \z/oxms) {
            $_ = '\r';
        }
        elsif (/\A ([\x00-\x20\x7F-\xFF]) \z/oxms) {
            $_ = sprintf('\x%02X', CORE::ord $1);
        }
        elsif (/\A [\x00-\xFF] \z/oxms) {
            $_ = quotemeta $_;
        }
    }

    # return character list
    return \@singleoctet, \@multipleoctet;
}

#
# KOI8-U octal escape sequence
#
sub octchr {
    my($octdigit) = @_;

    my @binary = ();
    for my $octal (split(//,$octdigit)) {
        push @binary, {
            '0' => '000',
            '1' => '001',
            '2' => '010',
            '3' => '011',
            '4' => '100',
            '5' => '101',
            '6' => '110',
            '7' => '111',
        }->{$octal};
    }
    my $binary = join '', @binary;

    my $octchr = {
        #                1234567
        1 => pack('B*', "0000000$binary"),
        2 => pack('B*', "000000$binary"),
        3 => pack('B*', "00000$binary"),
        4 => pack('B*', "0000$binary"),
        5 => pack('B*', "000$binary"),
        6 => pack('B*', "00$binary"),
        7 => pack('B*', "0$binary"),
        0 => pack('B*', "$binary"),

    }->{CORE::length($binary) % 8};

    return $octchr;
}

#
# KOI8-U hexadecimal escape sequence
#
sub hexchr {
    my($hexdigit) = @_;

    my $hexchr = {
        1 => pack('H*', "0$hexdigit"),
        0 => pack('H*', "$hexdigit"),

    }->{CORE::length($_[0]) % 2};

    return $hexchr;
}

#
# KOI8-U open character list for qr
#
sub charlist_qr {

    my $modifier = pop @_;
    my @char = @_;

    my($singleoctet, $multipleoctet) = _charlist(@char, $modifier);
    my @singleoctet   = @$singleoctet;
    my @multipleoctet = @$multipleoctet;

    # return character list
    if (scalar(@singleoctet) >= 1) {

        # with /i modifier
        if ($modifier =~ m/i/oxms) {
            my %singleoctet_ignorecase = ();
            for (@singleoctet) {
                while (s/ \A \\x(..) - \\x(..) //oxms or s/ \A \\x((..)) //oxms) {
                    for my $ord (hex($1) .. hex($2)) {
                        my $char = CORE::chr($ord);
                        my $uc = Ekoi8u::uc($char);
                        my $fc = Ekoi8u::fc($char);
                        if ($uc eq $fc) {
                            $singleoctet_ignorecase{unpack 'C*', $char} = 1;
                        }
                        else {
                            if (CORE::length($fc) == 1) {
                                $singleoctet_ignorecase{unpack 'C*', $uc} = 1;
                                $singleoctet_ignorecase{unpack 'C*', $fc} = 1;
                            }
                            else {
                                $singleoctet_ignorecase{unpack 'C*', $uc} = 1;
                                push @multipleoctet, join '', map {sprintf('\x%02X',$_)} unpack 'C*', $fc;
                            }
                        }
                    }
                }
                if ($_ ne '') {
                    $singleoctet_ignorecase{unpack 'C*', $_} = 1;
                }
            }
            my $i = 0;
            my @singleoctet_ignorecase = ();
            for my $ord (0 .. 255) {
                if (exists $singleoctet_ignorecase{$ord}) {
                    push @{$singleoctet_ignorecase[$i]}, $ord;
                }
                else {
                    $i++;
                }
            }
            @singleoctet = ();
            for my $range (@singleoctet_ignorecase) {
                if (ref $range) {
                    if (scalar(@{$range}) == 1) {
                        push @singleoctet, sprintf('\x%02X', @{$range}[0]);
                    }
                    elsif (scalar(@{$range}) == 2) {
                        push @singleoctet, sprintf('\x%02X\x%02X', @{$range}[0], @{$range}[-1]);
                    }
                    else {
                        push @singleoctet, sprintf('\x%02X-\x%02X', @{$range}[0], @{$range}[-1]);
                    }
                }
            }
        }

        my $not_anchor = '';

        push @multipleoctet, join('', $not_anchor, '[', @singleoctet, ']' );
    }
    if (scalar(@multipleoctet) >= 2) {
        return '(?:' . join('|', @multipleoctet) . ')';
    }
    else {
        return $multipleoctet[0];
    }
}

#
# KOI8-U open character list for not qr
#
sub charlist_not_qr {

    my $modifier = pop @_;
    my @char = @_;

    my($singleoctet, $multipleoctet) = _charlist(@char, $modifier);
    my @singleoctet   = @$singleoctet;
    my @multipleoctet = @$multipleoctet;

    # with /i modifier
    if ($modifier =~ m/i/oxms) {
        my %singleoctet_ignorecase = ();
        for (@singleoctet) {
            while (s/ \A \\x(..) - \\x(..) //oxms or s/ \A \\x((..)) //oxms) {
                for my $ord (hex($1) .. hex($2)) {
                    my $char = CORE::chr($ord);
                    my $uc = Ekoi8u::uc($char);
                    my $fc = Ekoi8u::fc($char);
                    if ($uc eq $fc) {
                        $singleoctet_ignorecase{unpack 'C*', $char} = 1;
                    }
                    else {
                        if (CORE::length($fc) == 1) {
                            $singleoctet_ignorecase{unpack 'C*', $uc} = 1;
                            $singleoctet_ignorecase{unpack 'C*', $fc} = 1;
                        }
                        else {
                            $singleoctet_ignorecase{unpack 'C*', $uc} = 1;
                            push @multipleoctet, join '', map {sprintf('\x%02X',$_)} unpack 'C*', $fc;
                        }
                    }
                }
            }
            if ($_ ne '') {
                $singleoctet_ignorecase{unpack 'C*', $_} = 1;
            }
        }
        my $i = 0;
        my @singleoctet_ignorecase = ();
        for my $ord (0 .. 255) {
            if (exists $singleoctet_ignorecase{$ord}) {
                push @{$singleoctet_ignorecase[$i]}, $ord;
            }
            else {
                $i++;
            }
        }
        @singleoctet = ();
        for my $range (@singleoctet_ignorecase) {
            if (ref $range) {
                if (scalar(@{$range}) == 1) {
                    push @singleoctet, sprintf('\x%02X', @{$range}[0]);
                }
                elsif (scalar(@{$range}) == 2) {
                    push @singleoctet, sprintf('\x%02X\x%02X', @{$range}[0], @{$range}[-1]);
                }
                else {
                    push @singleoctet, sprintf('\x%02X-\x%02X', @{$range}[0], @{$range}[-1]);
                }
            }
        }
    }

    # return character list
    if (scalar(@multipleoctet) >= 1) {
        if (scalar(@singleoctet) >= 1) {

            # any character other than multiple-octet and single octet character class
            return '(?!' . join('|', @multipleoctet) . ')(?:[^' . join('', @singleoctet) . '])';
        }
        else {

            # any character other than multiple-octet character class
            return '(?!' . join('|', @multipleoctet) . ")(?:$your_char)";
        }
    }
    else {
        if (scalar(@singleoctet) >= 1) {

            # any character other than single octet character class
            return                                      '(?:[^' . join('', @singleoctet) . '])';
        }
        else {

            # any character
            return                                      "(?:$your_char)";
        }
    }
}

#
# open file in read mode
#
sub _open_r {
    my(undef,$file) = @_;
    use Fcntl qw(O_RDONLY);
    return CORE::sysopen($_[0], $file, &O_RDONLY);
}

#
# open file in append mode
#
sub _open_a {
    my(undef,$file) = @_;
    use Fcntl qw(O_WRONLY O_APPEND O_CREAT);
    return CORE::sysopen($_[0], $file, &O_WRONLY|&O_APPEND|&O_CREAT);
}

#
# safe system
#
sub _systemx {

    # P.707 29.2.33. exec
    # in Chapter 29: Functions
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.
    #
    # Be aware that in older releases of Perl, exec (and system) did not flush
    # your output buffer, so you needed to enable command buffering by setting $|
    # on one or more filehandles to avoid lost output in the case of exec, or
    # misordererd output in the case of system. This situation was largely remedied
    # in the 5.6 release of Perl. (So, 5.005 release not yet.)

    # P.855 exec
    # in Chapter 27: Functions
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.
    #
    # In very old release of Perl (before v5.6), exec (and system) did not flush
    # your output buffer, so you needed to enable command buffering by setting $|
    # on one or more filehandles to avoid lost output with exec or misordered
    # output with system.

    $| = 1;

    # P.565 23.1.2. Cleaning Up Your Environment
    # in Chapter 23: Security
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.656 Cleaning Up Your Environment
    # in Chapter 20: Security
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    # local $ENV{'PATH'} = '.';
    local @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # Make %ENV safer

    # P.707 29.2.33. exec
    # in Chapter 29: Functions
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.
    #
    # As we mentioned earlier, exec treats a discrete list of arguments as an
    # indication that it should bypass shell processing. However, there is one
    # place where you might still get tripped up. The exec call (and system, too)
    # will not distinguish between a single scalar argument and an array containing
    # only one element.
    #
    #     @args = ("echo surprise");  # just one element in list
    #     exec @args                  # still subject to shell escapes
    #         or die "exec: $!";      #   because @args == 1
    #
    # To avoid this, you can use the PATHNAME syntax, explicitly duplicating the
    # first argument as the pathname, which forces the rest of the arguments to be
    # interpreted as a list, even if there is only one of them:
    #
    #     exec { $args[0] } @args  # safe even with one-argument list
    #         or die "can't exec @args: $!";

    # P.855 exec
    # in Chapter 27: Functions
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.
    #
    # As we mentioned earlier, exec treats a discrete list of arguments as a
    # directive to bypass shell processing. However, there is one place where
    # you might still get tripped up. The exec call (and system, too) cannot
    # distinguish between a single scalar argument and an array containing
    # only one element.
    #
    #     @args = ("echo surprise");  # just one element in list
    #     exec @args                  # still subject to shell escapes
    #         || die "exec: $!";      #   because @args == 1
    #
    # To avoid this, use the PATHNAME syntax, explicitly duplicating the first
    # argument as the pathname, which forces the rest of the arguments to be
    # interpreted as a list, even if there is only one of them:
    #
    #     exec { $args[0] } @args  # safe even with one-argument list
    #         || die "can't exec @args: $!";

    return CORE::system { $_[0] } @_; # safe even with one-argument list
}

#
# KOI8-U order to character (with parameter)
#
sub Ekoi8u::chr(;$) {

    my $c = @_ ? $_[0] : $_;

    if ($c == 0x00) {
        return "\x00";
    }
    else {
        my @chr = ();
        while ($c > 0) {
            unshift @chr, ($c % 0x100);
            $c = int($c / 0x100);
        }
        return pack 'C*', @chr;
    }
}

#
# KOI8-U order to character (without parameter)
#
sub Ekoi8u::chr_() {

    my $c = $_;

    if ($c == 0x00) {
        return "\x00";
    }
    else {
        my @chr = ();
        while ($c > 0) {
            unshift @chr, ($c % 0x100);
            $c = int($c / 0x100);
        }
        return pack 'C*', @chr;
    }
}

#
# KOI8-U path globbing (with parameter)
#
sub Ekoi8u::glob($) {

    if (wantarray) {
        my @glob = _DOS_like_glob(@_);
        for my $glob (@glob) {
            $glob =~ s{ \A (?:\./)+ }{}oxms;
        }
        return @glob;
    }
    else {
        my $glob = _DOS_like_glob(@_);
        $glob =~ s{ \A (?:\./)+ }{}oxms;
        return $glob;
    }
}

#
# KOI8-U path globbing (without parameter)
#
sub Ekoi8u::glob_() {

    if (wantarray) {
        my @glob = _DOS_like_glob();
        for my $glob (@glob) {
            $glob =~ s{ \A (?:\./)+ }{}oxms;
        }
        return @glob;
    }
    else {
        my $glob = _DOS_like_glob();
        $glob =~ s{ \A (?:\./)+ }{}oxms;
        return $glob;
    }
}

#
# KOI8-U path globbing via File::DosGlob 1.10
#
# Often I confuse "_dosglob" and "_doglob".
# So, I renamed "_dosglob" to "_DOS_like_glob".
#
my %iter;
my %entries;
sub _DOS_like_glob {

    # context (keyed by second cxix argument provided by core)
    my($expr,$cxix) = @_;

    # glob without args defaults to $_
    $expr = $_ if not defined $expr;

    # represents the current user's home directory
    #
    # 7.3. Expanding Tildes in Filenames
    # in Chapter 7. File Access
    # of ISBN 0-596-00313-7 Perl Cookbook, 2nd Edition.
    #
    # and File::HomeDir, File::HomeDir::Windows module

    # DOS-like system
    if ($^O =~ /\A (?: MSWin32 | NetWare | symbian | dos ) \z/oxms) {
        $expr =~ s{ \A ~ (?= [^/\\] ) }
                  { my_home_MSWin32() }oxmse;
    }

    # UNIX-like system
    else {
        $expr =~ s{ \A ~ ( (?:[^/])* ) }
                  { $1 ? (CORE::eval(q{(getpwnam($1))[7]})||my_home()) : my_home() }oxmse;
    }

    # assume global context if not provided one
    $cxix = '_G_' if not defined $cxix;
    $iter{$cxix} = 0 if not exists $iter{$cxix};

    # if we're just beginning, do it all first
    if ($iter{$cxix} == 0) {
            $entries{$cxix} = [ _do_glob(1, _parse_line($expr)) ];
    }

    # chuck it all out, quick or slow
    if (wantarray) {
        delete $iter{$cxix};
        return @{delete $entries{$cxix}};
    }
    else {
        if ($iter{$cxix} = scalar @{$entries{$cxix}}) {
            return shift @{$entries{$cxix}};
        }
        else {
            # return undef for EOL
            delete $iter{$cxix};
            delete $entries{$cxix};
            return undef;
        }
    }
}

#
# KOI8-U path globbing subroutine
#
sub _do_glob {

    my($cond,@expr) = @_;
    my @glob = ();
    my $fix_drive_relative_paths = 0;

OUTER:
    for my $expr (@expr) {
        next OUTER if not defined $expr;
        next OUTER if $expr eq '';

        my @matched = ();
        my @globdir = ();
        my $head    = '.';
        my $pathsep = '/';
        my $tail;

        # if argument is within quotes strip em and do no globbing
        if ($expr =~ /\A " ((?:$q_char)*?) " \z/oxms) {
            $expr = $1;
            if ($cond eq 'd') {
                if (-d $expr) {
                    push @glob, $expr;
                }
            }
            else {
                if (-e $expr) {
                    push @glob, $expr;
                }
            }
            next OUTER;
        }

        # wildcards with a drive prefix such as h:*.pm must be changed
        # to h:./*.pm to expand correctly
        if ($^O =~ /\A (?: MSWin32 | NetWare | symbian | dos ) \z/oxms) {
            if ($expr =~ s# \A ((?:[A-Za-z]:)?) ([^/\\]) #$1./$2#oxms) {
                $fix_drive_relative_paths = 1;
            }
        }

        if (($head, $tail) = _parse_path($expr,$pathsep)) {
            if ($tail eq '') {
                push @glob, $expr;
                next OUTER;
            }
            if ($head =~ / \A (?:$q_char)*? [*?] /oxms) {
                if (@globdir = _do_glob('d', $head)) {
                    push @glob, _do_glob($cond, map {"$_$pathsep$tail"} @globdir);
                    next OUTER;
                }
            }
            if ($head eq '' or $head =~ /\A [A-Za-z]: \z/oxms) {
                $head .= $pathsep;
            }
            $expr = $tail;
        }

        # If file component has no wildcards, we can avoid opendir
        if ($expr !~ / \A (?:$q_char)*? [*?] /oxms) {
            if ($head eq '.') {
                $head = '';
            }
            if ($head ne '' and ($head =~ / \G ($q_char) /oxmsg)[-1] ne $pathsep) {
                $head .= $pathsep;
            }
            $head .= $expr;
            if ($cond eq 'd') {
                if (-d $head) {
                    push @glob, $head;
                }
            }
            else {
                if (-e $head) {
                    push @glob, $head;
                }
            }
            next OUTER;
        }
        opendir(*DIR, $head) or next OUTER;
        my @leaf = readdir DIR;
        closedir DIR;

        if ($head eq '.') {
            $head = '';
        }
        if ($head ne '' and ($head =~ / \G ($q_char) /oxmsg)[-1] ne $pathsep) {
            $head .= $pathsep;
        }

        my $pattern = '';
        while ($expr =~ / \G ($q_char) /oxgc) {
            my $char = $1;

            # 6.9. Matching Shell Globs as Regular Expressions
            # in Chapter 6. Pattern Matching
            # of ISBN 0-596-00313-7 Perl Cookbook, 2nd Edition.
            # (and so on)

            if ($char eq '*') {
                $pattern .= "(?:$your_char)*",
            }
            elsif ($char eq '?') {
                $pattern .= "(?:$your_char)?",  # DOS style
#               $pattern .= "(?:$your_char)",   # UNIX style
            }
            elsif ((my $fc = Ekoi8u::fc($char)) ne $char) {
                $pattern .= $fc;
            }
            else {
                $pattern .= quotemeta $char;
            }
        }
        my $matchsub = sub { Ekoi8u::fc($_[0]) =~ /\A $pattern \z/xms };

#       if ($@) {
#           print STDERR "$0: $@\n";
#           next OUTER;
#       }

INNER:
        for my $leaf (@leaf) {
            if ($leaf eq '.' or $leaf eq '..') {
                next INNER;
            }
            if ($cond eq 'd' and not -d "$head$leaf") {
                next INNER;
            }

            if (&$matchsub($leaf)) {
                push @matched, "$head$leaf";
                next INNER;
            }

            # [DOS compatibility special case]
            # Failed, add a trailing dot and try again, but only...

            if (Ekoi8u::index($leaf,'.') == -1 and   # if name does not have a dot in it *and*
                CORE::length($leaf) <= 8 and        # name is shorter than or equal to 8 chars *and*
                Ekoi8u::index($pattern,'\\.') != -1  # pattern has a dot.
            ) {
                if (&$matchsub("$leaf.")) {
                    push @matched, "$head$leaf";
                    next INNER;
                }
            }
        }
        if (@matched) {
            push @glob, @matched;
        }
    }
    if ($fix_drive_relative_paths) {
        for my $glob (@glob) {
            $glob =~ s# \A ([A-Za-z]:) \./ #$1#oxms;
        }
    }
    return @glob;
}

#
# KOI8-U parse line
#
sub _parse_line {

    my($line) = @_;

    $line .= ' ';
    my @piece = ();
    while ($line =~ /
        " ( (?>(?: [^"]   )* ) ) " (?>\s+) |
          ( (?>(?: [^"\s] )* ) )   (?>\s+)
        /oxmsg
    ) {
        push @piece, defined($1) ? $1 : $2;
    }
    return @piece;
}

#
# KOI8-U parse path
#
sub _parse_path {

    my($path,$pathsep) = @_;

    $path .= '/';
    my @subpath = ();
    while ($path =~ /
        ((?: [^\/\\] )+?) [\/\\]
        /oxmsg
    ) {
        push @subpath, $1;
    }

    my $tail = pop @subpath;
    my $head = join $pathsep, @subpath;
    return $head, $tail;
}

#
# via File::HomeDir::Windows 1.00
#
sub my_home_MSWin32 {

    # A lot of unix people and unix-derived tools rely on
    # the ability to overload HOME. We will support it too
    # so that they can replace raw HOME calls with File::HomeDir.
    if (exists $ENV{'HOME'} and $ENV{'HOME'}) {
        return $ENV{'HOME'};
    }

    # Do we have a user profile?
    elsif (exists $ENV{'USERPROFILE'} and $ENV{'USERPROFILE'}) {
        return $ENV{'USERPROFILE'};
    }

    # Some Windows use something like $ENV{'HOME'}
    elsif (exists $ENV{'HOMEDRIVE'} and exists $ENV{'HOMEPATH'} and $ENV{'HOMEDRIVE'} and $ENV{'HOMEPATH'}) {
        return join '', $ENV{'HOMEDRIVE'}, $ENV{'HOMEPATH'};
    }

    return undef;
}

#
# via File::HomeDir::Unix 1.00
#
sub my_home {
    my $home;

    if (exists $ENV{'HOME'} and defined $ENV{'HOME'}) {
        $home = $ENV{'HOME'};
    }

    # This is from the original code, but I'm guessing
    # it means "login directory" and exists on some Unixes.
    elsif (exists $ENV{'LOGDIR'} and $ENV{'LOGDIR'}) {
        $home = $ENV{'LOGDIR'};
    }

    ### More-desperate methods

    # Light desperation on any (Unixish) platform
    else {
        $home = CORE::eval q{ (getpwuid($<))[7] };
    }

    # On Unix in general, a non-existant home means "no home"
    # For example, "nobody"-like users might use /nonexistant
    if (defined $home and ! -d($home)) {
        $home = undef;
    }
    return $home;
}

#
# ${^PREMATCH}, $PREMATCH, $` the string preceding what was matched
#
sub Ekoi8u::PREMATCH {
    return $`;
}

#
# ${^MATCH}, $MATCH, $& the string that matched
#
sub Ekoi8u::MATCH {
    return $&;
}

#
# ${^POSTMATCH}, $POSTMATCH, $' the string following what was matched
#
sub Ekoi8u::POSTMATCH {
    return $';
}

#
# KOI8-U character to order (with parameter)
#
sub KOI8U::ord(;$) {

    local $_ = shift if @_;

    if (/\A ($q_char) /oxms) {
        my @ord = unpack 'C*', $1;
        my $ord = 0;
        while (my $o = shift @ord) {
            $ord = $ord * 0x100 + $o;
        }
        return $ord;
    }
    else {
        return CORE::ord $_;
    }
}

#
# KOI8-U character to order (without parameter)
#
sub KOI8U::ord_() {

    if (/\A ($q_char) /oxms) {
        my @ord = unpack 'C*', $1;
        my $ord = 0;
        while (my $o = shift @ord) {
            $ord = $ord * 0x100 + $o;
        }
        return $ord;
    }
    else {
        return CORE::ord $_;
    }
}

#
# KOI8-U reverse
#
sub KOI8U::reverse(@) {

    if (wantarray) {
        return CORE::reverse @_;
    }
    else {

        # One of us once cornered Larry in an elevator and asked him what
        # problem he was solving with this, but he looked as far off into
        # the distance as he could in an elevator and said, "It seemed like
        # a good idea at the time."

        return join '', CORE::reverse(join('',@_) =~ /\G ($q_char) /oxmsg);
    }
}

#
# KOI8-U getc (with parameter, without parameter)
#
sub KOI8U::getc(;*@) {

    my($package) = caller;
    my $fh = @_ ? qualify_to_ref(shift,$package) : \*STDIN;
    croak 'Too many arguments for KOI8U::getc' if @_ and not wantarray;

    my @length = sort { $a <=> $b } keys %range_tr;
    my $getc = '';
    for my $length ($length[0] .. $length[-1]) {
        $getc .= CORE::getc($fh);
        if (exists $range_tr{CORE::length($getc)}) {
            if ($getc =~ /\A ${Ekoi8u::dot_s} \z/oxms) {
                return wantarray ? ($getc,@_) : $getc;
            }
        }
    }
    return wantarray ? ($getc,@_) : $getc;
}

#
# KOI8-U length by character
#
sub KOI8U::length(;$) {

    local $_ = shift if @_;

    local @_ = /\G ($q_char) /oxmsg;
    return scalar @_;
}

#
# KOI8-U substr by character
#
BEGIN {

    # P.232 The lvalue Attribute
    # in Chapter 6: Subroutines
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.336 The lvalue Attribute
    # in Chapter 7: Subroutines
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    # P.144 8.4 Lvalue subroutines
    # in Chapter 8: perlsub: Perl subroutines
    # of ISBN-13: 978-1-906966-02-7 The Perl Language Reference Manual (for Perl version 5.12.1)

    CORE::eval sprintf(<<'END', ($] >= 5.014000) ? ':lvalue' : '');
    #                       vv----------------------*******
    sub KOI8U::substr($$;$$) %s {

        my @char = $_[0] =~ /\G (?>$q_char) /oxmsg;

        # If the substring is beyond either end of the string, substr() returns the undefined
        # value and produces a warning. When used as an lvalue, specifying a substring that
        # is entirely outside the string raises an exception.
        # http://perldoc.perl.org/functions/substr.html

        # A return with no argument returns the scalar value undef in scalar context,
        # an empty list () in list context, and (naturally) nothing at all in void
        # context.

        my $offset = $_[1];
        if (($offset > scalar(@char)) or ($offset < (-1 * scalar(@char)))) {
            return;
        }

        # substr($string,$offset,$length,$replacement)
        if (@_ == 4) {
            my(undef,undef,$length,$replacement) = @_;
            my $substr = join '', splice(@char, $offset, $length, $replacement);
            $_[0] = join '', @char;

            # return $substr; this doesn't work, don't say "return"
            $substr;
        }

        # substr($string,$offset,$length)
        elsif (@_ == 3) {
            my(undef,undef,$length) = @_;
            my $octet_offset = 0;
            my $octet_length = 0;
            if ($offset == 0) {
                $octet_offset = 0;
            }
            elsif ($offset > 0) {
                local $SIG{__WARN__} = sub {}; # avoid: Use of uninitialized value in join or string at here
                $octet_offset =      CORE::length(join '', @char[0..$offset-1]);
            }
            else {
                local $SIG{__WARN__} = sub {}; # avoid: Use of uninitialized value in join or string at here
                $octet_offset = -1 * CORE::length(join '', @char[$#char+$offset+1..$#char]);
            }
            if ($length == 0) {
                $octet_length = 0;
            }
            elsif ($length > 0) {
                local $SIG{__WARN__} = sub {}; # avoid: Use of uninitialized value in join or string at here
                $octet_length =      CORE::length(join '', @char[$offset..$offset+$length-1]);
            }
            else {
                local $SIG{__WARN__} = sub {}; # avoid: Use of uninitialized value in join or string at here
                $octet_length = -1 * CORE::length(join '', @char[$#char+$length+1..$#char]);
            }
            CORE::substr($_[0], $octet_offset, $octet_length);
        }

        # substr($string,$offset)
        else {
            my $octet_offset = 0;
            if ($offset == 0) {
                $octet_offset = 0;
            }
            elsif ($offset > 0) {
                $octet_offset =      CORE::length(join '', @char[0..$offset-1]);
            }
            else {
                $octet_offset = -1 * CORE::length(join '', @char[$#char+$offset+1..$#char]);
            }
            CORE::substr($_[0], $octet_offset);
        }
    }
END
}

#
# KOI8-U index by character
#
sub KOI8U::index($$;$) {

    my $index;
    if (@_ == 3) {
        $index = Ekoi8u::index($_[0], $_[1], CORE::length(KOI8U::substr($_[0], 0, $_[2])));
    }
    else {
        $index = Ekoi8u::index($_[0], $_[1]);
    }

    if ($index == -1) {
        return -1;
    }
    else {
        return KOI8U::length(CORE::substr $_[0], 0, $index);
    }
}

#
# KOI8-U rindex by character
#
sub KOI8U::rindex($$;$) {

    my $rindex;
    if (@_ == 3) {
        $rindex = Ekoi8u::rindex($_[0], $_[1], CORE::length(KOI8U::substr($_[0], 0, $_[2])));
    }
    else {
        $rindex = Ekoi8u::rindex($_[0], $_[1]);
    }

    if ($rindex == -1) {
        return -1;
    }
    else {
        return KOI8U::length(CORE::substr $_[0], 0, $rindex);
    }
}

# when 'm//', '/' means regexp match 'm//' and '?' means regexp match '??'
# when 'div', '/' means division operator and '?' means conditional operator (condition ? then : else)
use vars qw($slash); $slash = 'm//';

# ord() to ord() or KOI8U::ord()
my $function_ord = 'ord';

# ord to ord or KOI8U::ord_
my $function_ord_ = 'ord';

# reverse to reverse or KOI8U::reverse
my $function_reverse = 'reverse';

# getc to getc or KOI8U::getc
my $function_getc = 'getc';

# P.1023 Appendix W.9 Multibyte Anchoring
# of ISBN 1-56592-224-7 CJKV Information Processing

my $anchor = '';

use vars qw($nest);

# regexp of nested parens in qqXX

# P.340 Matching Nested Constructs with Embedded Code
# in Chapter 7: Perl
# of ISBN 0-596-00289-0 Mastering Regular Expressions, Second edition

my $qq_paren   = qr{(?{local $nest=0}) (?>(?:
                       [^\\()] |
                           \(  (?{$nest++}) |
                           \)  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    \\ [^c] |
                    \\c[\x40-\x5F] |
                       [\x00-\xFF]
                 }xms;

my $qq_brace   = qr{(?{local $nest=0}) (?>(?:
                       [^\\{}] |
                           \{  (?{$nest++}) |
                           \}  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    \\ [^c] |
                    \\c[\x40-\x5F] |
                       [\x00-\xFF]
                 }xms;

my $qq_bracket = qr{(?{local $nest=0}) (?>(?:
                       [^\\\[\]] |
                           \[  (?{$nest++}) |
                           \]  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    \\ [^c] |
                    \\c[\x40-\x5F] |
                       [\x00-\xFF]
                 }xms;

my $qq_angle   = qr{(?{local $nest=0}) (?>(?:
                       [^\\<>] |
                           \<  (?{$nest++}) |
                           \>  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    \\ [^c] |
                    \\c[\x40-\x5F] |
                       [\x00-\xFF]
                 }xms;

my $qq_scalar  = qr{(?: \{ (?:$qq_brace)*? \} |
                       (?: ::)? (?:
                             (?> [a-zA-Z_][a-zA-Z_0-9]* (?: ::[a-zA-Z_][a-zA-Z_0-9]*)* )
                                                    (?>(?:                                   \[ (?: \$\[ | \$\] | $qq_char )*? \] |           \{ (?:$qq_brace)*? \} )*)
                                      (?>(?: (?: -> )? (?: [\$\@\%\&\*]\* | \$\#\* | [\@\%]? \[ (?: \$\[ | \$\] | $qq_char )*? \] | [\@\%\*]? \{ (?:$qq_brace)*? \} ) )*)
                   ))
                 }xms;

my $qq_variable = qr{(?: \{ (?:$qq_brace)*? \}                    |
                        (?: ::)? (?:
                              (?>[0-9]+)                          |
                              [^a-zA-Z_0-9\[\]] |
                              ^[A-Z]                              |
                              (?> [a-zA-Z_][a-zA-Z_0-9]* (?: ::[a-zA-Z_][a-zA-Z_0-9]*)* )
                                                     (?>(?:                                   \[ (?: \$\[ | \$\] | $qq_char )*? \] |           \{ (?:$qq_brace)*? \} )*)
                                       (?>(?: (?: -> )? (?: [\$\@\%\&\*]\* | \$\#\* | [\@\%]? \[ (?: \$\[ | \$\] | $qq_char )*? \] | [\@\%\*]? \{ (?:$qq_brace)*? \} ) )*)
                    ))
                  }xms;

my $qq_substr  = qr{(?> Char::substr | KOI8U::substr | CORE::substr | substr ) (?>\s*) \( $qq_paren \)
                 }xms;

# regexp of nested parens in qXX
my $q_paren    = qr{(?{local $nest=0}) (?>(?:
                       [^()] |
                             \(  (?{$nest++}) |
                             \)  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                       [\x00-\xFF]
                 }xms;

my $q_brace    = qr{(?{local $nest=0}) (?>(?:
                       [^\{\}] |
                             \{  (?{$nest++}) |
                             \}  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                       [\x00-\xFF]
                 }xms;

my $q_bracket  = qr{(?{local $nest=0}) (?>(?:
                       [^\[\]] |
                             \[  (?{$nest++}) |
                             \]  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    [\x00-\xFF]
                 }xms;

my $q_angle    = qr{(?{local $nest=0}) (?>(?:
                    [^<>] |
                             \<  (?{$nest++}) |
                             \>  (?(?{$nest>0})(?{$nest--})|(?!)))*) (?(?{$nest!=0})(?!)) |
                    [\x00-\xFF]
                 }xms;

my $matched     = '';
my $s_matched   = '';

my $tr_variable   = '';   # variable of tr///
my $sub_variable  = '';   # variable of s///
my $bind_operator = '';   # =~ or !~

my @heredoc = ();         # here document
my @heredoc_delimiter = ();
my $here_script = '';     # here script

#
# escape KOI8-U script
#
sub KOI8U::escape(;$) {
    local($_) = $_[0] if @_;

    # P.359 The Study Function
    # in Chapter 7: Perl
    # of ISBN 0-596-00289-0 Mastering Regular Expressions, Second edition

    study $_; # Yes, I studied study yesterday.

    # while all script

    # 6.14. Matching from Where the Last Pattern Left Off
    # in Chapter 6. Pattern Matching
    # of ISBN 0-596-00313-7 Perl Cookbook, 2nd Edition.
    # (and so on)

    # one member of Tag-team
    #
    # P.128 Start of match (or end of previous match): \G
    # P.130 Advanced Use of \G with Perl
    # in Chapter 3: Overview of Regular Expression Features and Flavors
    # P.255 Use leading anchors
    # P.256 Expose ^ and \G at the front expressions
    # in Chapter 6: Crafting an Efficient Expression
    # P.315 "Tag-team" matching with /gc
    # in Chapter 7: Perl
    # of ISBN 0-596-00289-0 Mastering Regular Expressions, Second edition

    my $e_script = '';
    while (not /\G \z/oxgc) { # member
        $e_script .= KOI8U::escape_token();
    }

    return $e_script;
}

#
# escape KOI8-U token of script
#
sub KOI8U::escape_token {

# \n output here document

    my $ignore_modules = join('|', qw(
        utf8
        bytes
        charnames
        I18N::Japanese
        I18N::Collate
        I18N::JExt
        File::DosGlob
        Wild
        Wildcard
        Japanese
    ));

    # another member of Tag-team
    #
    # P.315 "Tag-team" matching with /gc
    # in Chapter 7: Perl
    # of ISBN 0-596-00289-0 Mastering Regular Expressions, Second edition

    if (/\G ( \n ) /oxgc) { # another member (and so on)
        my $heredoc = '';
        if (scalar(@heredoc_delimiter) >= 1) {
            $slash = 'm//';

            $heredoc = join '', @heredoc;
            @heredoc = ();

            # skip here document
            for my $heredoc_delimiter (@heredoc_delimiter) {
                /\G .*? \n $heredoc_delimiter \n/xmsgc;
            }
            @heredoc_delimiter = ();

            $here_script = '';
        }
        return "\n" . $heredoc;
    }

# ignore space, comment
    elsif (/\G ((?>\s+)|\#.*) /oxgc) { return $1; }

# if (, elsif (, unless (, while (, until (, given (, and when (

    # given, when

    # P.225 The given Statement
    # in Chapter 15: Smart Matching and given-when
    # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

    # P.133 The given Statement
    # in Chapter 4: Statements and Declarations
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    elsif (/\G ( (?: if | elsif | unless | while | until | given | when ) (?>\s*) \( ) /oxgc) {
        $slash = 'm//';
        return $1;
    }

# scalar variable ($scalar = ...) =~ tr///;
# scalar variable ($scalar = ...) =~ s///;

    # state

    # P.68 Persistent, Private Variables
    # in Chapter 4: Subroutines
    # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

    # P.160 Persistent Lexically Scoped Variables: state
    # in Chapter 4: Statements and Declarations
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    # (and so on)

    elsif (/\G ( \( (?>\s*) (?: local \b | my \b | our \b | state \b )? (?>\s*) \$ $qq_scalar ) /oxgc) {
        my $e_string = e_string($1);

        if (/\G ( (?>\s*) = $qq_paren \) ) ( (?>\s*) (?: =~ | !~ ) (?>\s*) ) (?= (?: tr | y ) \b ) /oxgc) {
            $tr_variable = $e_string . e_string($1);
            $bind_operator = $2;
            $slash = 'm//';
            return '';
        }
        elsif (/\G ( (?>\s*) = $qq_paren \) ) ( (?>\s*) (?: =~ | !~ ) (?>\s*) ) (?= s \b ) /oxgc) {
            $sub_variable = $e_string . e_string($1);
            $bind_operator = $2;
            $slash = 'm//';
            return '';
        }
        else {
            $slash = 'div';
            return $e_string;
        }
    }

# $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
    elsif (/\G ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  \b | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) /oxmsgc) {
        $slash = 'div';
        return q{Ekoi8u::PREMATCH()};
    }

# $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
    elsif (/\G ( \$& | \$\{&\} | \$ (?>\s*) MATCH     \b | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) /oxmsgc) {
        $slash = 'div';
        return q{Ekoi8u::MATCH()};
    }

# $', ${'} --> $', ${'}
    elsif (/\G ( \$' | \$\{'\}                                                                                                     ) /oxmsgc) {
        $slash = 'div';
        return $1;
    }

# $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
    elsif (/\G (                 \$ (?>\s*) POSTMATCH \b | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) /oxmsgc) {
        $slash = 'div';
        return q{Ekoi8u::POSTMATCH()};
    }

# scalar variable $scalar =~ tr///;
# scalar variable $scalar =~ s///;
# substr() =~ tr///;
# substr() =~ s///;
    elsif (/\G ( \$ $qq_scalar | $qq_substr ) /oxgc) {
        my $scalar = e_string($1);

        if (/\G (    (?>\s*) (?: =~ | !~ ) (?>\s*) ) (?= (?: tr | y ) \b ) /oxgc) {
            $tr_variable = $scalar;
            $bind_operator = $1;
            $slash = 'm//';
            return '';
        }
        elsif (/\G ( (?>\s*) (?: =~ | !~ ) (?>\s*) ) (?= s            \b ) /oxgc) {
            $sub_variable = $scalar;
            $bind_operator = $1;
            $slash = 'm//';
            return '';
        }
        else {
            $slash = 'div';
            return $scalar;
        }
    }

    # end of statement
    elsif (/\G ( [,;] ) /oxgc) {
        $slash = 'm//';

        # clear tr/// variable
        $tr_variable  = '';

        # clear s/// variable
        $sub_variable  = '';

        $bind_operator = '';

        return $1;
    }

# bareword
    elsif (/\G ( \{ (?>\s*) (?: tr | index | rindex | reverse ) (?>\s*) \} ) /oxmsgc) {
        return $1;
    }

# $0 --> $0
    elsif (/\G ( \$ 0 ) /oxmsgc) {
        $slash = 'div';
        return $1;
    }
    elsif (/\G ( \$ \{ (?>\s*) 0 (?>\s*) \} ) /oxmsgc) {
        $slash = 'div';
        return $1;
    }

# $$ --> $$
    elsif (/\G ( \$ \$ ) (?![\w\{]) /oxmsgc) {
        $slash = 'div';
        return $1;
    }

# $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
# $1, $2, $3 --> $1, $2, $3 otherwise
    elsif (/\G \$ ((?>[1-9][0-9]*)) /oxmsgc) {
        $slash = 'div';
        return e_capture($1);
    }
    elsif (/\G \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} /oxmsgc) {
        $slash = 'div';
        return e_capture($1);
    }

# $$foo[ ... ] --> $ $foo->[ ... ]
    elsif (/\G \$ ( \$ (?> [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ .+? \] ) /oxmsgc) {
        $slash = 'div';
        return e_capture($1.'->'.$2);
    }

# $$foo{ ... } --> $ $foo->{ ... }
    elsif (/\G \$ ( \$ (?> [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ .+? \} ) /oxmsgc) {
        $slash = 'div';
        return e_capture($1.'->'.$2);
    }

# $$foo
    elsif (/\G \$ ( \$ (?> [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) /oxmsgc) {
        $slash = 'div';
        return e_capture($1);
    }

# ${ foo }
    elsif (/\G \$ (?>\s*) \{ ( (?>\s*) (?> [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* ) (?>\s*) ) \} /oxmsgc) {
        $slash = 'div';
        return '${' . $1 . '}';
    }

# ${ ... }
    elsif (/\G \$ (?>\s*) \{ (?>\s*) ( $qq_brace ) (?>\s*) \} /oxmsgc) {
        $slash = 'div';
        return e_capture($1);
    }

# variable or function
    #                  $ @ % & *     $ #
    elsif (/\G ( (?: [\$\@\%\&\*] | \$\# | -> | \b sub \b) (?>\s*) (?: split | chop | index | rindex | lc | uc | fc | chr | ord | reverse | getc | tr | y | q | qq | qx | qw | m | s | qr | glob | lstat | opendir | stat | unlink | chdir ) ) \b /oxmsgc) {
        $slash = 'div';
        return $1;
    }
    #                $ $ $ $ $ $ $ $ $ $ $ $ $ $
    #                $ @ # \ ' " / ? ( ) [ ] < >
    elsif (/\G ( \$[\$\@\#\\\'\"\/\?\(\)\[\]\<\>] ) /oxmsgc) {
        $slash = 'div';
        return $1;
    }

# while ()
    elsif (/\G \b (while (?>\s*) \( (?>\s*) <[\$]?[A-Za-z_][A-Za-z_0-9]*> (?>\s*) \)) \b /oxgc) {
        return $1;
    }

# while () --- glob

    # avoid "Error: Runtime exception" of perl version 5.005_03

    elsif (/\G \b while (?>\s*) \( (?>\s*) < ((?:[^>\0\a\e\f\n\r\t])+?) > (?>\s*) \) \b /oxgc) {
        return 'while ($_ = Ekoi8u::glob("' . $1 . '"))';
    }

# while (glob)
    elsif (/\G \b while (?>\s*) \( (?>\s*) glob (?>\s*) \) /oxgc) {
        return 'while ($_ = Ekoi8u::glob_)';
    }

# while (glob(WILDCARD))
    elsif (/\G \b while (?>\s*) \( (?>\s*) glob \b /oxgc) {
        return 'while ($_ = Ekoi8u::glob';
    }

# doit if, doit unless, doit while, doit until, doit for, doit when
    elsif (/\G \b ( if | unless | while | until | for | when ) \b /oxgc) { $slash = 'm//'; return $1; }

# subroutines of package Ekoi8u
    elsif (/\G \b (CORE:: | ->(>?\s*) (?: atan2 | [a-z]{2,})) \b       /oxgc) { $slash = 'm//'; return $1;                  }
    elsif (/\G \b Char::eval       (?= (?>\s*) \{ )                    /oxgc) { $slash = 'm//'; return 'eval';              }
    elsif (/\G \b KOI8U::eval       (?= (?>\s*) \{ )                    /oxgc) { $slash = 'm//'; return 'eval';              }
    elsif (/\G \b Char::eval    \b (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'eval Char::escape'; }
    elsif (/\G \b KOI8U::eval    \b (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'eval KOI8U::escape'; }
    elsif (/\G \b bytes::substr \b (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'substr';            }
    elsif (/\G \b chop \b          (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'Ekoi8u::chop';       }
    elsif (/\G \b bytes::index \b  (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'index';             }
    elsif (/\G \b Char::index \b   (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'Char::index';       }
    elsif (/\G \b KOI8U::index \b   (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'KOI8U::index';       }
    elsif (/\G \b index \b         (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'Ekoi8u::index';      }
    elsif (/\G \b bytes::rindex \b (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'rindex';            }
    elsif (/\G \b Char::rindex \b  (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'Char::rindex';      }
    elsif (/\G \b KOI8U::rindex \b  (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'KOI8U::rindex';      }
    elsif (/\G \b rindex \b        (?! (?>\s*) => )                    /oxgc) { $slash = 'm//'; return 'Ekoi8u::rindex';     }
    elsif (/\G \b lc      (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::lc';         }
    elsif (/\G \b lcfirst (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::lcfirst';    }
    elsif (/\G \b uc      (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::uc';         }
    elsif (/\G \b ucfirst (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::ucfirst';    }
    elsif (/\G \b fc      (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::fc';         }

    # "-s '' ..." means file test "-s 'filename' ..." (not means "- s/// ...")
    elsif (/\G -s                                          (?>\s*) (\") ((?:$qq_char)+?)               (\") /oxgc) { $slash = 'm//'; return '-s ' . e_qq('',  $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\#) ((?:$qq_char)+?)               (\#) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\() ((?:$qq_paren)+?)              (\)) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\{) ((?:$qq_brace)+?)              (\}) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\[) ((?:$qq_bracket)+?)            (\]) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\<) ((?:$qq_angle)+?)              (\>) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }
    elsif (/\G -s                               (?>\s+) qq (?>\s*) (\S) ((?:$qq_char)+?)               (\1) /oxgc) { $slash = 'm//'; return '-s ' . e_qq('qq',$1,$3,$2); }

    elsif (/\G -s                                          (?>\s*) (\') ((?:\\\'|\\\\|$q_char)+?)      (\') /oxgc) { $slash = 'm//'; return '-s ' . e_q ('',  $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\#) ((?:\\\#|\\\\|$q_char)+?)      (\#) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\() ((?:\\\)|\\\\|$q_paren)+?)     (\)) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\{) ((?:\\\}|\\\\|$q_brace)+?)     (\}) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\[) ((?:\\\]|\\\\|$q_bracket)+?)   (\]) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\<) ((?:\\\>|\\\\|$q_angle)+?)     (\>) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }
    elsif (/\G -s                               (?>\s+) q  (?>\s*) (\S) ((?:\\\1|\\\\|$q_char)+?)      (\1) /oxgc) { $slash = 'm//'; return '-s ' . e_q ('q', $1,$3,$2); }

    elsif (/\G -s                               (?>\s*) (\$ (?> \w+ (?: ::\w+)* ) (?: (?: ->)? (?: [\$\@\%\&\*]\* | \$\#\* | \( (?:$qq_paren)*? \) | [\@\%\*]? \{ (?:$qq_brace)+? \} | [\@\%]? \[ (?:$qq_bracket)+? \] ) )*) /oxgc)
                                                                                                                   { $slash = 'm//'; return "-s $1";   }
    elsif (/\G -s                               (?>\s*) \( ((?:$qq_paren)*?) \)                             /oxgc) { $slash = 'm//'; return "-s ($1)"; }
    elsif (/\G -s                               (?= (?>\s+) [a-z]+)                                         /oxgc) { $slash = 'm//'; return '-s';      }
    elsif (/\G -s                               (?>\s+) ((?>\w+))                                           /oxgc) { $slash = 'm//'; return "-s $1";   }

    elsif (/\G \b bytes::length (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'length';                   }
    elsif (/\G \b bytes::chr    (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'chr';                      }
    elsif (/\G \b chr           (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::chr';               }
    elsif (/\G \b bytes::ord    (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'div'; return 'ord';                      }
    elsif (/\G \b ord           (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'div'; return $function_ord;              }
    elsif (/\G \b glob          (?= (?>\s+)[A-Za-z_]|(?>\s*)['"`\$\@\&\*\(]) /oxgc) { $slash = 'm//'; return 'Ekoi8u::glob';              }
    elsif (/\G \b lc \b            (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::lc_';               }
    elsif (/\G \b lcfirst \b       (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::lcfirst_';          }
    elsif (/\G \b uc \b            (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::uc_';               }
    elsif (/\G \b ucfirst \b       (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::ucfirst_';          }
    elsif (/\G \b fc \b            (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::fc_';               }
    elsif (/\G    -s \b            (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return '-s ';                      }

    elsif (/\G \b bytes::length \b (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'length';                   }
    elsif (/\G \b bytes::chr \b    (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'chr';                      }
    elsif (/\G \b chr \b           (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::chr_';              }
    elsif (/\G \b bytes::ord \b    (?! (?>\s*) => )                          /oxgc) { $slash = 'div'; return 'ord';                      }
    elsif (/\G \b ord \b           (?! (?>\s*) => )                          /oxgc) { $slash = 'div'; return $function_ord_;             }
    elsif (/\G \b glob \b          (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return 'Ekoi8u::glob_';             }
    elsif (/\G \b reverse \b       (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return $function_reverse;          }
    elsif (/\G \b getc \b          (?! (?>\s*) => )                          /oxgc) { $slash = 'm//'; return $function_getc;             }
# split
    elsif (/\G \b (split) \b (?! (?>\s*) => ) /oxgc) {
        $slash = 'm//';

        my $e = '';
        while (/\G ( (?>\s+) | \( | \#.* ) /oxgc) {
            $e .= $1;
        }

# end of split
        if    (/\G (?= [,;\)\}\]] )          /oxgc) { return 'Ekoi8u::split' . $e;                 }

# split scalar value
        elsif (/\G ( [\$\@\&\*] $qq_scalar ) /oxgc) { return 'Ekoi8u::split' . $e . e_string($1);  }

# split literal space
        elsif (/\G \b qq           (\#) [ ] (\#) /oxgc) { return 'Ekoi8u::split' . $e . qq  {qq$1 $2}; }
        elsif (/\G \b qq ((?>\s*)) (\() [ ] (\)) /oxgc) { return 'Ekoi8u::split' . $e . qq{$1qq$2 $3}; }
        elsif (/\G \b qq ((?>\s*)) (\{) [ ] (\}) /oxgc) { return 'Ekoi8u::split' . $e . qq{$1qq$2 $3}; }
        elsif (/\G \b qq ((?>\s*)) (\[) [ ] (\]) /oxgc) { return 'Ekoi8u::split' . $e . qq{$1qq$2 $3}; }
        elsif (/\G \b qq ((?>\s*)) (\<) [ ] (\>) /oxgc) { return 'Ekoi8u::split' . $e . qq{$1qq$2 $3}; }
        elsif (/\G \b qq ((?>\s*)) (\S) [ ] (\2) /oxgc) { return 'Ekoi8u::split' . $e . qq{$1qq$2 $3}; }
        elsif (/\G \b q            (\#) [ ] (\#) /oxgc) { return 'Ekoi8u::split' . $e . qq   {q$1 $2}; }
        elsif (/\G \b q  ((?>\s*)) (\() [ ] (\)) /oxgc) { return 'Ekoi8u::split' . $e . qq {$1q$2 $3}; }
        elsif (/\G \b q  ((?>\s*)) (\{) [ ] (\}) /oxgc) { return 'Ekoi8u::split' . $e . qq {$1q$2 $3}; }
        elsif (/\G \b q  ((?>\s*)) (\[) [ ] (\]) /oxgc) { return 'Ekoi8u::split' . $e . qq {$1q$2 $3}; }
        elsif (/\G \b q  ((?>\s*)) (\<) [ ] (\>) /oxgc) { return 'Ekoi8u::split' . $e . qq {$1q$2 $3}; }
        elsif (/\G \b q  ((?>\s*)) (\S) [ ] (\2) /oxgc) { return 'Ekoi8u::split' . $e . qq {$1q$2 $3}; }
        elsif (/\G                    ' [ ] '    /oxgc) { return 'Ekoi8u::split' . $e . qq     {' '};  }
        elsif (/\G                    " [ ] "    /oxgc) { return 'Ekoi8u::split' . $e . qq     {" "};  }

# split qq//
        elsif (/\G \b (qq) \b /oxgc) {
            if (/\G (\#) ((?:$qq_char)*?) (\#) /oxgc)                        { return e_split($e.'qr',$1,$3,$2,'');   } # qq# #  --> qr # #
            else {
                while (not /\G \z/oxgc) {
                    if    (/\G ((?>\s+)|\#.*)                         /oxgc) { $e .= $1; }
                    elsif (/\G (\()          ((?:$qq_paren)*?)   (\)) /oxgc) { return e_split($e.'qr',$1,$3,$2,'');   } # qq ( ) --> qr ( )
                    elsif (/\G (\{)          ((?:$qq_brace)*?)   (\}) /oxgc) { return e_split($e.'qr',$1,$3,$2,'');   } # qq { } --> qr { }
                    elsif (/\G (\[)          ((?:$qq_bracket)*?) (\]) /oxgc) { return e_split($e.'qr',$1,$3,$2,'');   } # qq [ ] --> qr [ ]
                    elsif (/\G (\<)          ((?:$qq_angle)*?)   (\>) /oxgc) { return e_split($e.'qr',$1,$3,$2,'');   } # qq < > --> qr < >
                    elsif (/\G ([*\-:?\\^|]) ((?:$qq_char)*?)    (\1) /oxgc) { return e_split($e.'qr','{','}',$2,''); } # qq | | --> qr { }
                    elsif (/\G (\S)          ((?:$qq_char)*?)    (\1) /oxgc) { return e_split($e.'qr',$1,$3,$2,'');   } # qq * * --> qr * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# split qr//
        elsif (/\G \b (qr) \b /oxgc) {
            if (/\G (\#) ((?:$qq_char)*?) (\#) ([imosxpadlunbB]*) /oxgc)                        { return e_split  ($e.'qr',$1,$3,$2,$4);   } # qr# #
            else {
                while (not /\G \z/oxgc) {
                    if    (/\G ((?>\s+)|\#.*)                                            /oxgc) { $e .= $1; }
                    elsif (/\G (\()          ((?:$qq_paren)*?)   (\)) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # qr ( )
                    elsif (/\G (\{)          ((?:$qq_brace)*?)   (\}) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # qr { }
                    elsif (/\G (\[)          ((?:$qq_bracket)*?) (\]) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # qr [ ]
                    elsif (/\G (\<)          ((?:$qq_angle)*?)   (\>) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # qr < >
                    elsif (/\G (\')          ((?:$qq_char)*?)    (\') ([imosxpadlunbB]*) /oxgc) { return e_split_q($e.'qr',$1, $3, $2,$4); } # qr ' '
                    elsif (/\G ([*\-:?\\^|]) ((?:$qq_char)*?)    (\1) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr','{','}',$2,$4); } # qr | | --> qr { }
                    elsif (/\G (\S)          ((?:$qq_char)*?)    (\1) ([imosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # qr * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# split q//
        elsif (/\G \b (q) \b /oxgc) {
            if (/\G (\#) ((?:\\\#|\\\\|$q_char)*?) (\#) /oxgc)                    { return e_split_q($e.'qr',$1,$3,$2,'');   } # q# #  --> qr # #
            else {
                while (not /\G \z/oxgc) {
                    if    (/\G ((?>\s+)|\#.*)                              /oxgc) { $e .= $1; }
                    elsif (/\G (\() ((?:\\\\|\\\)|\\\(|$q_paren)*?)   (\)) /oxgc) { return e_split_q($e.'qr',$1,$3,$2,'');   } # q ( ) --> qr ( )
                    elsif (/\G (\{) ((?:\\\\|\\\}|\\\{|$q_brace)*?)   (\}) /oxgc) { return e_split_q($e.'qr',$1,$3,$2,'');   } # q { } --> qr { }
                    elsif (/\G (\[) ((?:\\\\|\\\]|\\\[|$q_bracket)*?) (\]) /oxgc) { return e_split_q($e.'qr',$1,$3,$2,'');   } # q [ ] --> qr [ ]
                    elsif (/\G (\<) ((?:\\\\|\\\>|\\\<|$q_angle)*?)   (\>) /oxgc) { return e_split_q($e.'qr',$1,$3,$2,'');   } # q < > --> qr < >
                    elsif (/\G ([*\-:?\\^|])       ((?:$q_char)*?)    (\1) /oxgc) { return e_split_q($e.'qr','{','}',$2,''); } # q | | --> qr { }
                    elsif (/\G (\S) ((?:\\\\|\\\1|     $q_char)*?)    (\1) /oxgc) { return e_split_q($e.'qr',$1,$3,$2,'');   } # q * * --> qr * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# split m//
        elsif (/\G \b (m) \b /oxgc) {
            if (/\G (\#) ((?:$qq_char)*?) (\#) ([cgimosxpadlunbB]*) /oxgc)                        { return e_split  ($e.'qr',$1,$3,$2,$4);   } # m# #  --> qr # #
            else {
                while (not /\G \z/oxgc) {
                    if    (/\G ((?>\s+)|\#.*)                                              /oxgc) { $e .= $1; }
                    elsif (/\G (\()          ((?:$qq_paren)*?)   (\)) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # m ( ) --> qr ( )
                    elsif (/\G (\{)          ((?:$qq_brace)*?)   (\}) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # m { } --> qr { }
                    elsif (/\G (\[)          ((?:$qq_bracket)*?) (\]) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # m [ ] --> qr [ ]
                    elsif (/\G (\<)          ((?:$qq_angle)*?)   (\>) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # m < > --> qr < >
                    elsif (/\G (\')          ((?:$qq_char)*?)    (\') ([cgimosxpadlunbB]*) /oxgc) { return e_split_q($e.'qr',$1, $3, $2,$4); } # m ' ' --> qr ' '
                    elsif (/\G ([*\-:?\\^|]) ((?:$qq_char)*?)    (\1) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr','{','}',$2,$4); } # m | | --> qr { }
                    elsif (/\G (\S)          ((?:$qq_char)*?)    (\1) ([cgimosxpadlunbB]*) /oxgc) { return e_split  ($e.'qr',$1, $3, $2,$4); } # m * * --> qr * *
                }
                die __FILE__, ": Search pattern not terminated\n";
            }
        }

# split ''
        elsif (/\G (\') /oxgc) {
            my $q_string = '';
            while (not /\G \z/oxgc) {
                if    (/\G (\\\\)    /oxgc) { $q_string .= $1; }
                elsif (/\G (\\\')    /oxgc) { $q_string .= $1; }                               # splitqr'' --> split qr''
                elsif (/\G \'        /oxgc)                                                    { return e_split_q($e.q{ qr},"'","'",$q_string,''); } # ' ' --> qr ' '
                elsif (/\G ($q_char) /oxgc) { $q_string .= $1; }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }

# split ""
        elsif (/\G (\") /oxgc) {
            my $qq_string = '';
            while (not /\G \z/oxgc) {
                if    (/\G (\\\\)    /oxgc) { $qq_string .= $1; }
                elsif (/\G (\\\")    /oxgc) { $qq_string .= $1; }                              # splitqr"" --> split qr""
                elsif (/\G \"        /oxgc)                                                    { return e_split($e.q{ qr},'"','"',$qq_string,''); } # " " --> qr " "
                elsif (/\G ($q_char) /oxgc) { $qq_string .= $1; }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }

# split //
        elsif (/\G (\/) /oxgc) {
            my $regexp = '';
            while (not /\G \z/oxgc) {
                if    (/\G (\\\\)                  /oxgc) { $regexp .= $1; }
                elsif (/\G (\\\/)                  /oxgc) { $regexp .= $1; }                   # splitqr// --> split qr//
                elsif (/\G \/ ([cgimosxpadlunbB]*) /oxgc)                                      { return e_split($e.q{ qr}, '/','/',$regexp,$1); } # / / --> qr / /
                elsif (/\G ($q_char)               /oxgc) { $regexp .= $1; }
            }
            die __FILE__, ": Search pattern not terminated\n";
        }
    }

# tr/// or y///

    # about [cdsrbB]* (/B modifier)
    #
    # P.559 appendix C
    # of ISBN 4-89052-384-7 Programming perl
    # (Japanese title is: Perl puroguramingu)

    elsif (/\G \b ( tr | y ) \b /oxgc) {
        my $ope = $1;

        #        $1   $2               $3   $4               $5   $6
        if (/\G (\#) ((?:$qq_char)*?) (\#) ((?:$qq_char)*?) (\#) ([cdsrbB]*) /oxgc) { # tr# # #
            my @tr = ($tr_variable,$2);
            return e_tr(@tr,'',$4,$6);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)              /oxgc) { $e .= $1; }
                elsif (/\G (\() ((?:$qq_paren)*?) (\)) /oxgc) {
                    my @tr = ($tr_variable,$2);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                            /oxgc) { $e .= $1; }
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr ( ) ( )
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr ( ) { }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr ( ) [ ]
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr ( ) < >
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr ( ) * *
                    }
                    die __FILE__, ": Transliteration replacement not terminated\n";
                }
                elsif (/\G (\{) ((?:$qq_brace)*?) (\}) /oxgc) {
                    my @tr = ($tr_variable,$2);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                            /oxgc) { $e .= $1; }
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr { } ( )
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr { } { }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr { } [ ]
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr { } < >
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr { } * *
                    }
                    die __FILE__, ": Transliteration replacement not terminated\n";
                }
                elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) {
                    my @tr = ($tr_variable,$2);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                            /oxgc) { $e .= $1; }
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr [ ] ( )
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr [ ] { }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr [ ] [ ]
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr [ ] < >
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr [ ] * *
                    }
                    die __FILE__, ": Transliteration replacement not terminated\n";
                }
                elsif (/\G (\<) ((?:$qq_angle)*?) (\>) /oxgc) {
                    my @tr = ($tr_variable,$2);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                            /oxgc) { $e .= $1; }
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr < > ( )
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr < > { }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr < > [ ]
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr < > < >
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cdsrbB]*) /oxgc) { return e_tr(@tr,$e,$2,$4); } # tr < > * *
                    }
                    die __FILE__, ": Transliteration replacement not terminated\n";
                }
                #           $1   $2               $3   $4               $5   $6
                elsif (/\G (\S) ((?:$qq_char)*?) (\1) ((?:$qq_char)*?) (\1) ([cdsrbB]*) /oxgc) { # tr * * *
                    my @tr = ($tr_variable,$2);
                    return e_tr(@tr,'',$4,$6);
                }
            }
            die __FILE__, ": Transliteration pattern not terminated\n";
        }
    }

# qq//
    elsif (/\G \b (qq) \b /oxgc) {
        my $ope = $1;

#       if (/\G (\#) ((?:$qq_char)*?) (\#) /oxgc) { return e_qq($ope,$1,$3,$2); } # qq# #
        if (/\G (\#) /oxgc) {                                                     # qq# #
            my $qq_string = '';
            while (not /\G \z/oxgc) {
                if    (/\G (\\\\)     /oxgc) { $qq_string .= $1;                     }
                elsif (/\G (\\\#)     /oxgc) { $qq_string .= $1;                     }
                elsif (/\G (\#)       /oxgc) { return e_qq($ope,'#','#',$qq_string); }
                elsif (/\G ($qq_char) /oxgc) { $qq_string .= $1;                     }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }

        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)              /oxgc) { $e .= $1; }

#               elsif (/\G (\() ((?:$qq_paren)*?) (\)) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qq ( )
                elsif (/\G (\() /oxgc) {                                                           # qq ( )
                    my $qq_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\\\))     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\()       /oxgc) { $qq_string .= $1; $nest++;                 }
                        elsif (/\G (\))       /oxgc) {
                            if (--$nest == 0)        { return $e . e_qq($ope,'(',')',$qq_string); }
                            else                     { $qq_string .= $1;                          }
                        }
                        elsif (/\G ($qq_char) /oxgc) { $qq_string .= $1;                          }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\{) ((?:$qq_brace)*?) (\}) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qq { }
                elsif (/\G (\{) /oxgc) {                                                           # qq { }
                    my $qq_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\\\})     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\{)       /oxgc) { $qq_string .= $1; $nest++;                 }
                        elsif (/\G (\})       /oxgc) {
                            if (--$nest == 0)        { return $e . e_qq($ope,'{','}',$qq_string); }
                            else                     { $qq_string .= $1;                          }
                        }
                        elsif (/\G ($qq_char) /oxgc) { $qq_string .= $1;                          }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qq [ ]
                elsif (/\G (\[) /oxgc) {                                                             # qq [ ]
                    my $qq_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\\\])     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\[)       /oxgc) { $qq_string .= $1; $nest++;                 }
                        elsif (/\G (\])       /oxgc) {
                            if (--$nest == 0)        { return $e . e_qq($ope,'[',']',$qq_string); }
                            else                     { $qq_string .= $1;                          }
                        }
                        elsif (/\G ($qq_char) /oxgc) { $qq_string .= $1;                          }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\<) ((?:$qq_angle)*?) (\>) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qq < >
                elsif (/\G (\<) /oxgc) {                                                           # qq < >
                    my $qq_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\\\>)     /oxgc) { $qq_string .= $1;                          }
                        elsif (/\G (\<)       /oxgc) { $qq_string .= $1; $nest++;                 }
                        elsif (/\G (\>)       /oxgc) {
                            if (--$nest == 0)        { return $e . e_qq($ope,'<','>',$qq_string); }
                            else                     { $qq_string .= $1;                          }
                        }
                        elsif (/\G ($qq_char) /oxgc) { $qq_string .= $1;                          }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\S) ((?:$qq_char)*?) (\1) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qq * *
                elsif (/\G (\S) /oxgc) {                                                          # qq * *
                    my $delimiter = $1;
                    my $qq_string = '';
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)             /oxgc) { $qq_string .= $1;                                        }
                        elsif (/\G (\\\Q$delimiter\E) /oxgc) { $qq_string .= $1;                                        }
                        elsif (/\G (\Q$delimiter\E)   /oxgc) { return $e . e_qq($ope,$delimiter,$delimiter,$qq_string); }
                        elsif (/\G ($qq_char)         /oxgc) { $qq_string .= $1;                                        }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }
    }

# qr//
    elsif (/\G \b (qr) \b /oxgc) {
        my $ope = $1;
        if (/\G (\#) ((?:$qq_char)*?) (\#) ([imosxpadlunbB]*) /oxgc) { # qr# # #
            return e_qr($ope,$1,$3,$2,$4);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)                                            /oxgc) { $e .= $1; }
                elsif (/\G (\()          ((?:$qq_paren)*?)   (\)) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # qr ( )
                elsif (/\G (\{)          ((?:$qq_brace)*?)   (\}) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # qr { }
                elsif (/\G (\[)          ((?:$qq_bracket)*?) (\]) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # qr [ ]
                elsif (/\G (\<)          ((?:$qq_angle)*?)   (\>) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # qr < >
                elsif (/\G (\')          ((?:$qq_char)*?)    (\') ([imosxpadlunbB]*) /oxgc) { return $e . e_qr_q($ope,$1, $3, $2,$4); } # qr ' '
                elsif (/\G ([*\-:?\\^|]) ((?:$qq_char)*?)    (\1) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,'{','}',$2,$4); } # qr | | --> qr { }
                elsif (/\G (\S)          ((?:$qq_char)*?)    (\1) ([imosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # qr * *
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }
    }

# qw//
    elsif (/\G \b (qw) \b /oxgc) {
        my $ope = $1;
        if (/\G (\#) (.*?) (\#) /oxmsgc) { # qw# #
            return e_qw($ope,$1,$3,$2);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)                        /oxgc)   { $e .= $1; }

                elsif (/\G (\()          ([^(]*?)           (\)) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw ( )
                elsif (/\G (\()          ((?:$q_paren)*?)   (\)) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw ( )

                elsif (/\G (\{)          ([^{]*?)           (\}) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw { }
                elsif (/\G (\{)          ((?:$q_brace)*?)   (\}) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw { }

                elsif (/\G (\[)          ([^[]*?)           (\]) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw [ ]
                elsif (/\G (\[)          ((?:$q_bracket)*?) (\]) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw [ ]

                elsif (/\G (\<)          ([^<]*?)           (\>) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw < >
                elsif (/\G (\<)          ((?:$q_angle)*?)   (\>) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw < >

                elsif (/\G ([\x21-\x3F]) (.*?)              (\1) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw * *
                elsif (/\G (\S)          ((?:$q_char)*?)    (\1) /oxmsgc) { return $e . e_qw($ope,$1,$3,$2); } # qw * *
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }
    }

# qx//
    elsif (/\G \b (qx) \b /oxgc) {
        my $ope = $1;
        if (/\G (\#) ((?:$qq_char)*?) (\#) /oxgc) { # qx# #
            return e_qq($ope,$1,$3,$2);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)                /oxgc) { $e .= $1; }
                elsif (/\G (\() ((?:$qq_paren)*?)   (\)) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qx ( )
                elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qx { }
                elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qx [ ]
                elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qx < >
                elsif (/\G (\') ((?:$qq_char)*?)    (\') /oxgc) { return $e . e_q ($ope,$1,$3,$2); } # qx ' '
                elsif (/\G (\S) ((?:$qq_char)*?)    (\1) /oxgc) { return $e . e_qq($ope,$1,$3,$2); } # qx * *
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }
    }

# q//
    elsif (/\G \b (q) \b /oxgc) {
        my $ope = $1;

#       if (/\G (\#) ((?:\\\#|\\\\|$q_char)*?) (\#) /oxgc) { return e_q($ope,$1,$3,$2); } # q# #

        # avoid "Error: Runtime exception" of perl version 5.005_03
        # (and so on)

        if (/\G (\#) /oxgc) {                                                             # q# #
            my $q_string = '';
            while (not /\G \z/oxgc) {
                if    (/\G (\\\\)    /oxgc) { $q_string .= $1;                    }
                elsif (/\G (\\\#)    /oxgc) { $q_string .= $1;                    }
                elsif (/\G (\#)      /oxgc) { return e_q($ope,'#','#',$q_string); }
                elsif (/\G ($q_char) /oxgc) { $q_string .= $1;                    }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }

        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)                       /oxgc) { $e .= $1; }

#               elsif (/\G (\() ((?:\\\)|\\\\|$q_paren)*?) (\)) /oxgc) { return $e . e_q($ope,$1,$3,$2); } # q ( )
                elsif (/\G (\() /oxgc) {                                                                   # q ( )
                    my $q_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\))    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\()    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\()      /oxgc) { $q_string .= $1; $nest++;                }
                        elsif (/\G (\))      /oxgc) {
                            if (--$nest == 0)       { return $e . e_q($ope,'(',')',$q_string); }
                            else                    { $q_string .= $1;                         }
                        }
                        elsif (/\G ($q_char) /oxgc) { $q_string .= $1;                         }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\{) ((?:\\\}|\\\\|$q_brace)*?) (\}) /oxgc) { return $e . e_q($ope,$1,$3,$2); } # q { }
                elsif (/\G (\{) /oxgc) {                                                                   # q { }
                    my $q_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\})    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\{)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\{)      /oxgc) { $q_string .= $1; $nest++;                }
                        elsif (/\G (\})      /oxgc) {
                            if (--$nest == 0)       { return $e . e_q($ope,'{','}',$q_string); }
                            else                    { $q_string .= $1;                         }
                        }
                        elsif (/\G ($q_char) /oxgc) { $q_string .= $1;                         }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\[) ((?:\\\]|\\\\|$q_bracket)*?) (\]) /oxgc) { return $e . e_q($ope,$1,$3,$2); } # q [ ]
                elsif (/\G (\[) /oxgc) {                                                                     # q [ ]
                    my $q_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\])    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\[)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\[)      /oxgc) { $q_string .= $1; $nest++;                }
                        elsif (/\G (\])      /oxgc) {
                            if (--$nest == 0)       { return $e . e_q($ope,'[',']',$q_string); }
                            else                    { $q_string .= $1;                         }
                        }
                        elsif (/\G ($q_char) /oxgc) { $q_string .= $1;                         }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\<) ((?:\\\>|\\\\|$q_angle)*?) (\>) /oxgc) { return $e . e_q($ope,$1,$3,$2); } # q < >
                elsif (/\G (\<) /oxgc) {                                                                   # q < >
                    my $q_string = '';
                    local $nest = 1;
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\>)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\\\<)    /oxgc) { $q_string .= $1;                         }
                        elsif (/\G (\<)      /oxgc) { $q_string .= $1; $nest++;                }
                        elsif (/\G (\>)      /oxgc) {
                            if (--$nest == 0)       { return $e . e_q($ope,'<','>',$q_string); }
                            else                    { $q_string .= $1;                         }
                        }
                        elsif (/\G ($q_char) /oxgc) { $q_string .= $1;                         }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }

#               elsif (/\G (\S) ((?:\\\1|\\\\|$q_char)*?) (\1) /oxgc) { return $e . e_q($ope,$1,$3,$2); } # q * *
                elsif (/\G (\S) /oxgc) {                                                                  # q * *
                    my $delimiter = $1;
                    my $q_string = '';
                    while (not /\G \z/oxgc) {
                        if    (/\G (\\\\)             /oxgc) { $q_string .= $1;                                       }
                        elsif (/\G (\\\Q$delimiter\E) /oxgc) { $q_string .= $1;                                       }
                        elsif (/\G (\Q$delimiter\E)   /oxgc) { return $e . e_q($ope,$delimiter,$delimiter,$q_string); }
                        elsif (/\G ($q_char)          /oxgc) { $q_string .= $1;                                       }
                    }
                    die __FILE__, ": Can't find string terminator anywhere before EOF\n";
                }
            }
            die __FILE__, ": Can't find string terminator anywhere before EOF\n";
        }
    }

# m//
    elsif (/\G \b (m) \b /oxgc) {
        my $ope = $1;
        if (/\G (\#) ((?:$qq_char)*?) (\#) ([cgimosxpadlunbB]*) /oxgc) { # m# #
            return e_qr($ope,$1,$3,$2,$4);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if    (/\G ((?>\s+)|\#.*)                                             /oxgc) { $e .= $1; }
                elsif (/\G (\()         ((?:$qq_paren)*?)   (\)) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m ( )
                elsif (/\G (\{)         ((?:$qq_brace)*?)   (\}) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m { }
                elsif (/\G (\[)         ((?:$qq_bracket)*?) (\]) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m [ ]
                elsif (/\G (\<)         ((?:$qq_angle)*?)   (\>) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m < >
                elsif (/\G (\?)         ((?:$qq_char)*?)    (\?) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m ? ?
                elsif (/\G (\')         ((?:$qq_char)*?)    (\') ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr_q($ope,$1, $3, $2,$4); } # m ' '
                elsif (/\G ([*\-:\\^|]) ((?:$qq_char)*?)    (\1) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,'{','}',$2,$4); } # m | | --> m { }
                elsif (/\G (\S)         ((?:$qq_char)*?)    (\1) ([cgimosxpadlunbB]*) /oxgc) { return $e . e_qr  ($ope,$1, $3, $2,$4); } # m * *
            }
            die __FILE__, ": Search pattern not terminated\n";
        }
    }

# s///

    # about [cegimosxpradlunbB]* (/cg modifier)
    #
    # P.67 Pattern-Matching Operators
    # of ISBN 0-596-00241-6 Perl in a Nutshell, Second Edition.

    elsif (/\G \b (s) \b /oxgc) {
        my $ope = $1;

        #        $1   $2               $3   $4               $5   $6
        if (/\G (\#) ((?:$qq_char)*?) (\#) ((?:$qq_char)*?) (\#) ([cegimosxpradlunbB]*) /oxgc) { # s# # #
            return e_sub($sub_variable,$1,$2,$3,$3,$4,$5,$6);
        }
        else {
            my $e = '';
            while (not /\G \z/oxgc) {
                if (/\G ((?>\s+)|\#.*) /oxgc) { $e .= $1; }
                elsif (/\G (\() ((?:$qq_paren)*?) (\)) /oxgc) {
                    my @s = ($1,$2,$3);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                                       /oxgc) { $e .= $1; }
                        #           $1   $2                  $3   $4
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\') ((?:$qq_char)*?)    (\') ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\$) ((?:$qq_char)*?)    (\$) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\:) ((?:$qq_char)*?)    (\:) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\@) ((?:$qq_char)*?)    (\@) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                    }
                    die __FILE__, ": Substitution replacement not terminated\n";
                }
                elsif (/\G (\{) ((?:$qq_brace)*?) (\}) /oxgc) {
                    my @s = ($1,$2,$3);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                                       /oxgc) { $e .= $1; }
                        #           $1   $2                  $3   $4
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\') ((?:$qq_char)*?)    (\') ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\$) ((?:$qq_char)*?)    (\$) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\:) ((?:$qq_char)*?)    (\:) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\@) ((?:$qq_char)*?)    (\@) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                    }
                    die __FILE__, ": Substitution replacement not terminated\n";
                }
                elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) {
                    my @s = ($1,$2,$3);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                                       /oxgc) { $e .= $1; }
                        #           $1   $2                  $3   $4
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\') ((?:$qq_char)*?)    (\') ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\$) ((?:$qq_char)*?)    (\$) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                    }
                    die __FILE__, ": Substitution replacement not terminated\n";
                }
                elsif (/\G (\<) ((?:$qq_angle)*?) (\>) /oxgc) {
                    my @s = ($1,$2,$3);
                    while (not /\G \z/oxgc) {
                        if    (/\G ((?>\s+)|\#.*)                                       /oxgc) { $e .= $1; }
                        #           $1   $2                  $3   $4
                        elsif (/\G (\() ((?:$qq_paren)*?)   (\)) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\{) ((?:$qq_brace)*?)   (\}) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\[) ((?:$qq_bracket)*?) (\]) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\<) ((?:$qq_angle)*?)   (\>) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\') ((?:$qq_char)*?)    (\') ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\$) ((?:$qq_char)*?)    (\$) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\:) ((?:$qq_char)*?)    (\:) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\@) ((?:$qq_char)*?)    (\@) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                        elsif (/\G (\S) ((?:$qq_char)*?)    (\1) ([cegimosxpradlunbB]*) /oxgc) { return e_sub($sub_variable,@s,$1,$2,$3,$4); }
                    }
                    die __FILE__, ": Substitution replacement not terminated\n";
                }
                #           $1   $2               $3   $4               $5   $6
                elsif (/\G (\') ((?:$qq_char)*?) (\') ((?:$qq_char)*?) (\') ([cegimosxpradlunbB]*) /oxgc) {
                    return e_sub($sub_variable,$1,$2,$3,$3,$4,$5,$6);
                }
                #           $1            $2               $3   $4               $5   $6
                elsif (/\G ([*\-:?\\^|]) ((?:$qq_char)*?) (\1) ((?:$qq_char)*?) (\1) ([cegimosxpradlunbB]*) /oxgc) {
                    return e_sub($sub_variable,'{',$2,'}','{',$4,'}',$6); # s | | | --> s { } { }
                }
                #           $1   $2               $3   $4               $5   $6
                elsif (/\G (\$) ((?:$qq_char)*?) (\1) ((?:$qq_char)*?) (\1) ([cegimosxpradlunbB]*) /oxgc) {
                    return e_sub($sub_variable,$1,$2,$3,$3,$4,$5,$6);
                }
                #           $1   $2               $3   $4               $5   $6
                elsif (/\G (\S) ((?:$qq_char)*?) (\1) ((?:$qq_char)*?) (\1) ([cegimosxpradlunbB]*) /oxgc) {
                    return e_sub($sub_variable,$1,$2,$3,$3,$4,$5,$6);
                }
            }
            die __FILE__, ": Substitution pattern not terminated\n";
        }
    }

# require ignore module
    elsif (/\G \b require ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [#\n])                  /oxmsgc) { return "# require$1$2";     }
    elsif (/\G \b require ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [^#]) /oxmsgc) { return "# require$1\n$2";   }
    elsif (/\G \b require ((?>\s+) (?:$ignore_modules)) \b                                    /oxmsgc) { return "# require$1";       }

# use strict; --> use strict; no strict qw(refs);
    elsif (/\G \b use ((?>\s+) strict .*? ;) ([ \t]* [#\n])                                   /oxmsgc) { return "use$1 no strict qw(refs);$2";   }
    elsif (/\G \b use ((?>\s+) strict .*? ;) ([ \t]* [^#])                  /oxmsgc) { return "use$1 no strict qw(refs);\n$2"; }
    elsif (/\G \b use ((?>\s+) strict) \b                                                     /oxmsgc) { return "use$1; no strict qw(refs)";     }

# use 5.12.0; --> use 5.12.0; no strict qw(refs);
    elsif (/\G \b use (?>\s+) ((?>([1-9][0-9_]*)(?:\.([0-9_]+))*))  (?>\s*) ; /oxmsgc) {
        if (($2 >= 6) or (($2 == 5) and ($3 ge '012'))) {
            return "use $1; no strict qw(refs);";
        }
        else {
            return "use $1;";
        }
    }
    elsif (/\G \b use (?>\s+) ((?>v([0-9][0-9_]*)(?:\.([0-9_]+))*)) (?>\s*) ; /oxmsgc) {
        if (($2 >= 6) or (($2 == 5) and ($3 >= 12))) {
            return "use $1; no strict qw(refs);";
        }
        else {
            return "use $1;";
        }
    }

# ignore use module
    elsif (/\G \b use ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [#\n])                  /oxmsgc) { return "# use$1$2";         }
    elsif (/\G \b use ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [^#]) /oxmsgc) { return "# use$1\n$2";       }
    elsif (/\G \b use ((?>\s+) (?:$ignore_modules)) \b                                    /oxmsgc) { return "# use$1";           }

# ignore no module
    elsif (/\G \b no  ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [#\n])                  /oxmsgc) { return "# no$1$2";          }
    elsif (/\G \b no  ((?>\s+) (?:$ignore_modules) .*? ;) ([ \t]* [^#]) /oxmsgc) { return "# no$1\n$2";        }
    elsif (/\G \b no  ((?>\s+) (?:$ignore_modules)) \b                                    /oxmsgc) { return "# no$1";            }

# use else
    elsif (/\G \b use \b /oxmsgc) { return "use"; }

# use else
    elsif (/\G \b no  \b /oxmsgc) { return "no";  }

# ''
    elsif (/\G (?
        my $q_string = '';
        while (not /\G \z/oxgc) {
            if    (/\G (\\\\)                  /oxgc) { $q_string .= $1;                   }
            elsif (/\G (\\\')                  /oxgc) { $q_string .= $1;                   }
            elsif (/\G \'                      /oxgc) { return e_q('', "'","'",$q_string); }
            elsif (/\G ($q_char)               /oxgc) { $q_string .= $1;                   }
        }
        die __FILE__, ": Can't find string terminator anywhere before EOF\n";
    }

# ""
    elsif (/\G (\") /oxgc) {
        my $qq_string = '';
        while (not /\G \z/oxgc) {
            if    (/\G (\\\\)                  /oxgc) { $qq_string .= $1;                    }
            elsif (/\G (\\\")                  /oxgc) { $qq_string .= $1;                    }
            elsif (/\G \"                      /oxgc) { return e_qq('', '"','"',$qq_string); }
            elsif (/\G ($q_char)               /oxgc) { $qq_string .= $1;                    }
        }
        die __FILE__, ": Can't find string terminator anywhere before EOF\n";
    }

# ``
    elsif (/\G (\`) /oxgc) {
        my $qx_string = '';
        while (not /\G \z/oxgc) {
            if    (/\G (\\\\)                  /oxgc) { $qx_string .= $1;                    }
            elsif (/\G (\\\`)                  /oxgc) { $qx_string .= $1;                    }
            elsif (/\G \`                      /oxgc) { return e_qq('', '`','`',$qx_string); }
            elsif (/\G ($q_char)               /oxgc) { $qx_string .= $1;                    }
        }
        die __FILE__, ": Can't find string terminator anywhere before EOF\n";
    }

# //   --- not divide operator (num / num), not defined-or
    elsif (($slash eq 'm//') and /\G (\/) /oxgc) {
        my $regexp = '';
        while (not /\G \z/oxgc) {
            if    (/\G (\\\\)                  /oxgc) { $regexp .= $1;                       }
            elsif (/\G (\\\/)                  /oxgc) { $regexp .= $1;                       }
            elsif (/\G \/ ([cgimosxpadlunbB]*) /oxgc) { return e_qr('', '/','/',$regexp,$1); }
            elsif (/\G ($q_char)               /oxgc) { $regexp .= $1;                       }
        }
        die __FILE__, ": Search pattern not terminated\n";
    }

# ??   --- not conditional operator (condition ? then : else)
    elsif (($slash eq 'm//') and /\G (\?) /oxgc) {
        my $regexp = '';
        while (not /\G \z/oxgc) {
            if    (/\G (\\\\)                  /oxgc) { $regexp .= $1;                       }
            elsif (/\G (\\\?)                  /oxgc) { $regexp .= $1;                       }
            elsif (/\G \? ([cgimosxpadlunbB]*) /oxgc) { return e_qr('m','?','?',$regexp,$1); }
            elsif (/\G ($q_char)               /oxgc) { $regexp .= $1;                       }
        }
        die __FILE__, ": Search pattern not terminated\n";
    }

# <<>> (a safer ARGV)
    elsif (/\G ( <<>> ) /oxgc)                         { $slash = 'm//'; return $1;          }

# << (bit shift)   --- not here document
    elsif (/\G ( << (?>\s*) ) (?= [0-9\$\@\&] ) /oxgc) { $slash = 'm//'; return $1;          }

# <<~'HEREDOC'
    elsif (/\G ( <<~ [\t ]* '([a-zA-Z_0-9]*)' ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n ([\t ]*) $delimiter \n //xms) {
            my $heredoc = $1;
            my $indent  = $2;
            $heredoc =~ s{^$indent}{}msg; # no /ox
            push @heredoc, $heredoc . qq{\n$delimiter\n};
            push @heredoc_delimiter, qq{\\s*$delimiter};
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return qq{<<'$delimiter'};
    }

# <<~\HEREDOC

    # P.66 2.6.6. "Here" Documents
    # in Chapter 2: Bits and Pieces
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.73 "Here" Documents
    # in Chapter 2: Bits and Pieces
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    elsif (/\G ( <<~ \\([a-zA-Z_0-9]+) ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n ([\t ]*) $delimiter \n //xms) {
            my $heredoc = $1;
            my $indent  = $2;
            $heredoc =~ s{^$indent}{}msg; # no /ox
            push @heredoc, $heredoc . qq{\n$delimiter\n};
            push @heredoc_delimiter, qq{\\s*$delimiter};
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return qq{<<\\$delimiter};
    }

# <<~"HEREDOC"
    elsif (/\G ( <<~ [\t ]* "([a-zA-Z_0-9]*)" ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n ([\t ]*) $delimiter \n //xms) {
            my $heredoc = $1;
            my $indent  = $2;
            $heredoc =~ s{^$indent}{}msg; # no /ox
            push @heredoc, e_heredoc($heredoc) . qq{\n$delimiter\n};
            push @heredoc_delimiter, qq{\\s*$delimiter};
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return qq{<<"$delimiter"};
    }

# <<~HEREDOC
    elsif (/\G ( <<~ ([a-zA-Z_0-9]+) ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n ([\t ]*) $delimiter \n //xms) {
            my $heredoc = $1;
            my $indent  = $2;
            $heredoc =~ s{^$indent}{}msg; # no /ox
            push @heredoc, e_heredoc($heredoc) . qq{\n$delimiter\n};
            push @heredoc_delimiter, qq{\\s*$delimiter};
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return qq{<<$delimiter};
    }

# <<~`HEREDOC`
    elsif (/\G ( <<~ [\t ]* `([a-zA-Z_0-9]*)` ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n ([\t ]*) $delimiter \n //xms) {
            my $heredoc = $1;
            my $indent  = $2;
            $heredoc =~ s{^$indent}{}msg; # no /ox
            push @heredoc, e_heredoc($heredoc) . qq{\n$delimiter\n};
            push @heredoc_delimiter, qq{\\s*$delimiter};
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return qq{<<`$delimiter`};
    }

# <<'HEREDOC'
    elsif (/\G ( << '([a-zA-Z_0-9]*)' ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n $delimiter \n //xms) {
            push @heredoc, $1 . qq{\n$delimiter\n};
            push @heredoc_delimiter, $delimiter;
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return $here_quote;
    }

# <<\HEREDOC

    # P.66 2.6.6. "Here" Documents
    # in Chapter 2: Bits and Pieces
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.73 "Here" Documents
    # in Chapter 2: Bits and Pieces
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    elsif (/\G ( << \\([a-zA-Z_0-9]+) ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n $delimiter \n //xms) {
            push @heredoc, $1 . qq{\n$delimiter\n};
            push @heredoc_delimiter, $delimiter;
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return $here_quote;
    }

# <<"HEREDOC"
    elsif (/\G ( << "([a-zA-Z_0-9]*)" ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n $delimiter \n //xms) {
            push @heredoc, e_heredoc($1) . qq{\n$delimiter\n};
            push @heredoc_delimiter, $delimiter;
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return $here_quote;
    }

# <
    elsif (/\G ( << ([a-zA-Z_0-9]+) ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n $delimiter \n //xms) {
            push @heredoc, e_heredoc($1) . qq{\n$delimiter\n};
            push @heredoc_delimiter, $delimiter;
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return $here_quote;
    }

# <<`HEREDOC`
    elsif (/\G ( << `([a-zA-Z_0-9]*)` ) /oxgc) {
        $slash = 'm//';
        my $here_quote = $1;
        my $delimiter  = $2;

        # get here document
        if ($here_script eq '') {
            $here_script = CORE::substr $_, pos $_;
            $here_script =~ s/.*?\n//oxm;
        }
        if ($here_script =~ s/\A (.*?) \n $delimiter \n //xms) {
            push @heredoc, e_heredoc($1) . qq{\n$delimiter\n};
            push @heredoc_delimiter, $delimiter;
        }
        else {
            die __FILE__, ": Can't find string terminator $delimiter anywhere before EOF\n";
        }
        return $here_quote;
    }

# <<= <=> <= < operator
    elsif (/\G ( <<= | <=> | <= | < ) (?= (?>\s*) [A-Za-z_0-9'"`\$\@\&\*\(\+\-] )/oxgc) {
        return $1;
    }

#
    elsif (/\G (<[\$]?[A-Za-z_][A-Za-z_0-9]*>) /oxgc) {
        return $1;
    }

#  --- glob

    # avoid "Error: Runtime exception" of perl version 5.005_03

    elsif (/\G < ((?:[^>\0\a\e\f\n\r\t])+?) > /oxgc) {
        return 'Ekoi8u::glob("' . $1 . '")';
    }

# __DATA__
    elsif (/\G ^ ( __DATA__ \n .*) \z /oxmsgc) { return $1; }

# __END__
    elsif (/\G ^ ( __END__  \n .*) \z /oxmsgc) { return $1; }

# \cD Control-D

    # P.68 2.6.8. Other Literal Tokens
    # in Chapter 2: Bits and Pieces
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.76 Other Literal Tokens
    # in Chapter 2: Bits and Pieces
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    elsif (/\G   ( \cD         .*) \z /oxmsgc) { return $1; }

# \cZ Control-Z
    elsif (/\G   ( \cZ         .*) \z /oxmsgc) { return $1; }

    # any operator before div
    elsif (/\G (
            -- | \+\+ |
            [\)\}\]]

            ) /oxgc) { $slash = 'div'; return $1; }

    # yada-yada or triple-dot operator
    elsif (/\G (
            \.\.\.

            ) /oxgc) { $slash = 'm//'; return q{die('Unimplemented')}; }

    # any operator before m//

    # //, //= (defined-or)

    # P.164 Logical Operators
    # in Chapter 10: More Control Structures
    # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

    # P.119 C-Style Logical (Short-Circuit) Operators
    # in Chapter 3: Unary and Binary Operators
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    # (and so on)

    # ~~

    # P.221 The Smart Match Operator
    # in Chapter 15: Smart Matching and given-when
    # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

    # P.112 Smartmatch Operator
    # in Chapter 3: Unary and Binary Operators
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    # (and so on)

    elsif (/\G ((?>

            !~~ | !~ | != | ! |
            %= | % |
            &&= | && | &= | &\.= | &\. | & |
            -= | -> | - |
            :(?>\s*)= |
            : |
            <<>> |
            <<= | <=> | <= | < |
            == | => | =~ | = |
            >>= | >> | >= | > |
            \*\*= | \*\* | \*= | \* |
            \+= | \+ |
            \.\. | \.= | \. |
            \/\/= | \/\/ |
            \/= | \/ |
            \? |
            \\ |
            \^= | \^\.= | \^\. | \^ |
            \b x= |
            \|\|= | \|\| | \|= | \|\.= | \|\. | \| |
            ~~ | ~\. | ~ |
            \b(?: and | cmp | eq | ge | gt | le | lt | ne | not | or | xor | x )\b |
            \b(?: print )\b |

            [,;\(\{\[]

            )) /oxgc) { $slash = 'm//'; return $1; }

    # other any character
    elsif (/\G ($q_char) /oxgc) { $slash = 'div'; return $1; }

    # system error
    else {
        die __FILE__, ": Oops, this shouldn't happen!\n";
    }
}

# escape KOI8-U string
sub e_string {
    my($string) = @_;
    my $e_string = '';

    local $slash = 'm//';

    # P.1024 Appendix W.10 Multibyte Processing
    # of ISBN 1-56592-224-7 CJKV Information Processing
    # (and so on)

    my @char = $string =~ / \G (?>[^\\]|\\$q_char|$q_char) /oxmsg;

    # without { ... }
    if (not (grep(/\A \{ \z/xms, @char) and grep(/\A \} \z/xms, @char))) {
        if ($string !~ /<
            return $string;
        }
    }

E_STRING_LOOP:
    while ($string !~ /\G \z/oxgc) {
        if (0) {
        }

# $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> @{[Ekoi8u::PREMATCH()]}
        elsif ($string =~ /\G ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  \b | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) /oxmsgc) {
            $e_string .= q{Ekoi8u::PREMATCH()};
            $slash = 'div';
        }

# $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> @{[Ekoi8u::MATCH()]}
        elsif ($string =~ /\G ( \$& | \$\{&\} | \$ (?>\s*) MATCH     \b | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) /oxmsgc) {
            $e_string .= q{Ekoi8u::MATCH()};
            $slash = 'div';
        }

# $', ${'} --> $', ${'}
        elsif ($string =~ /\G ( \$' | \$\{'\}                                                                                                     ) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }

# $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> @{[Ekoi8u::POSTMATCH()]}
        elsif ($string =~ /\G (                 \$ (?>\s*) POSTMATCH \b | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) /oxmsgc) {
            $e_string .= q{Ekoi8u::POSTMATCH()};
            $slash = 'div';
        }

# bareword
        elsif ($string =~ /\G ( \{ (?>\s*) (?: tr | index | rindex | reverse ) (?>\s*) \} ) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }

# $0 --> $0
        elsif ($string =~ /\G ( \$ 0 ) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }
        elsif ($string =~ /\G ( \$ \{ (?>\s*) 0 (?>\s*) \} ) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }

# $$ --> $$
        elsif ($string =~ /\G ( \$ \$ ) (?![\w\{]) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }

# $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
# $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($string =~ /\G \$ ((?>[1-9][0-9]*)) /oxmsgc) {
            $e_string .= e_capture($1);
            $slash = 'div';
        }
        elsif ($string =~ /\G \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} /oxmsgc) {
            $e_string .= e_capture($1);
            $slash = 'div';
        }

# $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($string =~ /\G \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ .+? \] ) /oxmsgc) {
            $e_string .= e_capture($1.'->'.$2);
            $slash = 'div';
        }

# $$foo{ ... } --> $ $foo->{ ... }
        elsif ($string =~ /\G \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ .+? \} ) /oxmsgc) {
            $e_string .= e_capture($1.'->'.$2);
            $slash = 'div';
        }

# $$foo
        elsif ($string =~ /\G \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) /oxmsgc) {
            $e_string .= e_capture($1);
            $slash = 'div';
        }

# ${ foo }
        elsif ($string =~ /\G \$ (?>\s*) \{ ((?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* )) \} /oxmsgc) {
            $e_string .= '${' . $1 . '}';
            $slash = 'div';
        }

# ${ ... }
        elsif ($string =~ /\G \$ (?>\s*) \{ (?>\s*) ( $qq_brace ) (?>\s*) \} /oxmsgc) {
            $e_string .= e_capture($1);
            $slash = 'div';
        }

# variable or function
        #                             $ @ % & *     $ #
        elsif ($string =~ /\G ( (?: [\$\@\%\&\*] | \$\# | -> | \b sub \b) (?>\s*) (?: split | chop | index | rindex | lc | uc | fc | chr | ord | reverse | getc | tr | y | q | qq | qx | qw | m | s | qr | glob | lstat | opendir | stat | unlink | chdir ) ) \b /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }
        #                           $ $ $ $ $ $ $ $ $ $ $ $ $ $
        #                           $ @ # \ ' " / ? ( ) [ ] < >
        elsif ($string =~ /\G ( \$[\$\@\#\\\'\"\/\?\(\)\[\]\<\>] ) /oxmsgc) {
            $e_string .= $1;
            $slash = 'div';
        }

# qq//
        elsif ($string =~ /\G \b (qq) \b /oxgc) {
            my $ope = $1;
            if ($string =~ /\G (\#) ((?:$qq_char)*?) (\#) /oxgc) { # qq# #
                $e_string .= e_qq($ope,$1,$3,$2);
            }
            else {
                my $e = '';
                while ($string !~ /\G \z/oxgc) {
                    if    ($string =~ /\G ((?>\s+)|\#.*)                /oxgc) { $e .= $1; }
                    elsif ($string =~ /\G (\() ((?:$qq_paren)*?)   (\)) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qq ( )
                    elsif ($string =~ /\G (\{) ((?:$qq_brace)*?)   (\}) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qq { }
                    elsif ($string =~ /\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qq [ ]
                    elsif ($string =~ /\G (\<) ((?:$qq_angle)*?)   (\>) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qq < >
                    elsif ($string =~ /\G (\S) ((?:$qq_char)*?)    (\1) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qq * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# qx//
        elsif ($string =~ /\G \b (qx) \b /oxgc) {
            my $ope = $1;
            if ($string =~ /\G (\#) ((?:$qq_char)*?) (\#) /oxgc) { # qx# #
                $e_string .= e_qq($ope,$1,$3,$2);
            }
            else {
                my $e = '';
                while ($string !~ /\G \z/oxgc) {
                    if    ($string =~ /\G ((?>\s+)|\#.*)                /oxgc) { $e .= $1; }
                    elsif ($string =~ /\G (\() ((?:$qq_paren)*?)   (\)) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qx ( )
                    elsif ($string =~ /\G (\{) ((?:$qq_brace)*?)   (\}) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qx { }
                    elsif ($string =~ /\G (\[) ((?:$qq_bracket)*?) (\]) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qx [ ]
                    elsif ($string =~ /\G (\<) ((?:$qq_angle)*?)   (\>) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qx < >
                    elsif ($string =~ /\G (\') ((?:$qq_char)*?)    (\') /oxgc) { $e_string .= $e . e_q ($ope,$1,$3,$2); next E_STRING_LOOP; } # qx ' '
                    elsif ($string =~ /\G (\S) ((?:$qq_char)*?)    (\1) /oxgc) { $e_string .= $e . e_qq($ope,$1,$3,$2); next E_STRING_LOOP; } # qx * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# q//
        elsif ($string =~ /\G \b (q) \b /oxgc) {
            my $ope = $1;
            if ($string =~ /\G (\#) ((?:\\\#|\\\\|$q_char)*?) (\#) /oxgc) { # q# #
                $e_string .= e_q($ope,$1,$3,$2);
            }
            else {
                my $e = '';
                while ($string !~ /\G \z/oxgc) {
                    if    ($string =~ /\G ((?>\s+)|\#.*)                              /oxgc) { $e .= $1; }
                    elsif ($string =~ /\G (\() ((?:\\\\|\\\)|\\\(|$q_paren)*?)   (\)) /oxgc) { $e_string .= $e . e_q($ope,$1,$3,$2); next E_STRING_LOOP; } # q ( )
                    elsif ($string =~ /\G (\{) ((?:\\\\|\\\}|\\\{|$q_brace)*?)   (\}) /oxgc) { $e_string .= $e . e_q($ope,$1,$3,$2); next E_STRING_LOOP; } # q { }
                    elsif ($string =~ /\G (\[) ((?:\\\\|\\\]|\\\[|$q_bracket)*?) (\]) /oxgc) { $e_string .= $e . e_q($ope,$1,$3,$2); next E_STRING_LOOP; } # q [ ]
                    elsif ($string =~ /\G (\<) ((?:\\\\|\\\>|\\\<|$q_angle)*?)   (\>) /oxgc) { $e_string .= $e . e_q($ope,$1,$3,$2); next E_STRING_LOOP; } # q < >
                    elsif ($string =~ /\G (\S) ((?:\\\\|\\\1|     $q_char)*?)    (\1) /oxgc) { $e_string .= $e . e_q($ope,$1,$3,$2); next E_STRING_LOOP; } # q * *
                }
                die __FILE__, ": Can't find string terminator anywhere before EOF\n";
            }
        }

# ''
        elsif ($string =~ /\G (?

# ""
        elsif ($string =~ /\G (\") ((?:$qq_char)*?) (\")                                        /oxgc) { $e_string .= e_qq('',$1,$3,$2); }

# ``
        elsif ($string =~ /\G (\`) ((?:$qq_char)*?) (\`)                                        /oxgc) { $e_string .= e_qq('',$1,$3,$2); }

        # other any character
        elsif ($string =~ /\G ($q_char) /oxgc) { $e_string .= $1; }

        # system error
        else {
            die __FILE__, ": Oops, this shouldn't happen!\n";
        }
    }

    return $e_string;
}

#
# character class
#
sub character_class {
    my($char,$modifier) = @_;

    if ($char eq '.') {
        if ($modifier =~ /s/) {
            return '${Ekoi8u::dot_s}';
        }
        else {
            return '${Ekoi8u::dot}';
        }
    }
    else {
        return Ekoi8u::classic_character_class($char);
    }
}

#
# escape capture ($1, $2, $3, ...)
#
sub e_capture {

    return join '', '${',                $_[0],  '}';
}

#
# escape transliteration (tr/// or y///)
#
sub e_tr {
    my($variable,$charclass,$e,$charclass2,$modifier) = @_;
    my $e_tr = '';
    $modifier ||= '';

    $slash = 'div';

    # quote character class 1
    $charclass  = q_tr($charclass);

    # quote character class 2
    $charclass2 = q_tr($charclass2);

    # /b /B modifier
    if ($modifier =~ tr/bB//d) {
        if ($variable eq '') {
            $e_tr = qq{tr$charclass$e$charclass2$modifier};
        }
        else {
            $e_tr = qq{$variable${bind_operator}tr$charclass$e$charclass2$modifier};
        }
    }
    else {
        if ($variable eq '') {
            $e_tr = qq{Ekoi8u::tr(\$_,' =~ ',$charclass,$e$charclass2,'$modifier')};
        }
        else {
            $e_tr = qq{Ekoi8u::tr($variable,'$bind_operator',$charclass,$e$charclass2,'$modifier')};
        }
    }

    # clear tr/// variable
    $tr_variable = '';
    $bind_operator = '';

    return $e_tr;
}

#
# quote for escape transliteration (tr/// or y///)
#
sub q_tr {
    my($charclass) = @_;

    # quote character class
    if ($charclass !~ /'/oxms) {
        return e_q('',  "'", "'", $charclass); # --> q' '
    }
    elsif ($charclass !~ /\//oxms) {
        return e_q('q',  '/', '/', $charclass); # --> q/ /
    }
    elsif ($charclass !~ /\#/oxms) {
        return e_q('q',  '#', '#', $charclass); # --> q# #
    }
    elsif ($charclass !~ /[\<\>]/oxms) {
        return e_q('q', '<', '>', $charclass); # --> q< >
    }
    elsif ($charclass !~ /[\(\)]/oxms) {
        return e_q('q', '(', ')', $charclass); # --> q( )
    }
    elsif ($charclass !~ /[\{\}]/oxms) {
        return e_q('q', '{', '}', $charclass); # --> q{ }
    }
    else {
        for my $char (qw( ! " $ % & * + . : = ? @ ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
            if ($charclass !~ /\Q$char\E/xms) {
                return e_q('q', $char, $char, $charclass);
            }
        }
    }

    return e_q('q', '{', '}', $charclass);
}

#
# escape q string (q//, '')
#
sub e_q {
    my($ope,$delimiter,$end_delimiter,$string) = @_;

    $slash = 'div';

    return join '', $ope, $delimiter, $string, $end_delimiter;
}

#
# escape qq string (qq//, "", qx//, ``)
#
sub e_qq {
    my($ope,$delimiter,$end_delimiter,$string) = @_;

    $slash = 'div';

    my $left_e  = 0;
    my $right_e = 0;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\$] |
        \\x\{ (?>[0-9A-Fa-f]+) \}            |
        \\o\{ (?>[0-7]+)       \}            |
        \\N\{ (?>[^0-9\}][^\}]*) \} |
        \\ $q_char                           |
        \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  |
        \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     |
                        \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} |
        \$ (?>\s* [0-9]+)                    |
        \$ (?>\s*) \{ (?>\s* [0-9]+ \s*) \}  |
        \$ \$ (?![\w\{])                     |
        \$ (?>\s*) \$ (?>\s*) $qq_variable   |
           $q_char
    ))/oxmsg;

    for (my $i=0; $i <= $#char; $i++) {

        # "\L\u" --> "\u\L"
        if (($char[$i] eq '\L') and ($char[$i+1] eq '\u')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # "\U\l" --> "\l\U"
        elsif (($char[$i] eq '\U') and ($char[$i+1] eq '\l')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::hexchr($1);
        }

        # \N{CHARNAME} --> N{CHARNAME}
        elsif ($char[$i] =~ /\A \\ ( N\{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1;
        }

        if (0) {
        }

        # \F
        #
        # P.69 Table 2-6. Translation escapes
        # in Chapter 2: Bits and Pieces
        # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.
        # (and so on)

        # \u \l \U \L \F \Q \E
        elsif ($char[$i] =~ /\A ([<>]) \z/oxms) {
            if ($right_e < $left_e) {
                $char[$i] = '\\' . $char[$i];
            }
        }
        elsif ($char[$i] eq '\u') {

            # "STRING @{[ LIST EXPR ]} MORE STRING"

            # P.257 Other Tricks You Can Do with Hard References
            # in Chapter 8: References
            # of ISBN 0-596-00027-8 Programming Perl Third Edition.

            # P.353 Other Tricks You Can Do with Hard References
            # in Chapter 8: References
            # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

            # (and so on)

            $char[$i] = '@{[Ekoi8u::ucfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\l') {
            $char[$i] = '@{[Ekoi8u::lcfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\U') {
            $char[$i] = '@{[Ekoi8u::uc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\L') {
            $char[$i] = '@{[Ekoi8u::lc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\F') {
            $char[$i] = '@{[Ekoi8u::fc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\Q') {
            $char[$i] = '@{[CORE::quotemeta qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\E') {
            if ($right_e < $left_e) {
                $char[$i] = '>]}';
                $right_e++;
            }
            else {
                $char[$i] = '';
            }
        }
        elsif ($char[$i] eq '\Q') {
            while (1) {
                if (++$i > $#char) {
                    last;
                }
                if ($char[$i] eq '\E') {
                    last;
                }
            }
        }
        elsif ($char[$i] eq '\E') {
        }

        # $0 --> $0
        elsif ($char[$i] =~ /\A \$ 0 \z/oxms) {
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) 0 (?>\s*) \} \z/oxms) {
        }

        # $$ --> $$
        elsif ($char[$i] =~ /\A \$\$ \z/oxms) {
        }

        # $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
        # $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($char[$i] =~ /\A \$ ((?>[1-9][0-9]*)) \z/oxms) {
            $char[$i] = e_capture($1);
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
            $char[$i] = e_capture($1);
        }

        # $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ (?:$qq_bracket)*? \] ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
        }

        # $$foo{ ... } --> $ $foo->{ ... }
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ (?:$qq_brace)*? \} ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
        }

        # $$foo
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) \z/oxms) {
            $char[$i] = e_capture($1);
        }

        # $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
        elsif ($char[$i] =~ /\A ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH (?>\s*) \}  | \$ (?>\s*) \{\^PREMATCH\}  ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::PREMATCH()]}';
        }

        # $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
        elsif ($char[$i] =~ /\A ( \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::MATCH()]}';
        }

        # $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
        elsif ($char[$i] =~ /\A (                 \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::POSTMATCH()]}';
        }

        # ${ foo } --> ${ foo }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ (?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* ) \}                                \z/oxms) {
        }

        # ${ ... }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ( .+ ) \} \z/oxms) {
            $char[$i] = e_capture($1);
        }
    }

    # return string
    if ($left_e > $right_e) {
        return join '', $ope, $delimiter, @char, '>]}' x ($left_e - $right_e), $end_delimiter;
    }
    return     join '', $ope, $delimiter, @char,                               $end_delimiter;
}

#
# escape qw string (qw//)
#
sub e_qw {
    my($ope,$delimiter,$end_delimiter,$string) = @_;

    $slash = 'div';

    # choice again delimiter
    my %octet = map {$_ => 1} ($string =~ /\G ([\x00-\xFF]) /oxmsg);
    if (not $octet{$end_delimiter}) {
        return join '', $ope, $delimiter, $string, $end_delimiter;
    }
    elsif (not $octet{')'}) {
        return join '', $ope, '(',        $string, ')';
    }
    elsif (not $octet{'}'}) {
        return join '', $ope, '{',        $string, '}';
    }
    elsif (not $octet{']'}) {
        return join '', $ope, '[',        $string, ']';
    }
    elsif (not $octet{'>'}) {
        return join '', $ope, '<',        $string, '>';
    }
    else {
        for my $char (qw( ! " $ % & * + - . / : = ? @ ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
            if (not $octet{$char}) {
                return join '', $ope,      $char, $string, $char;
            }
        }
    }

    # qw/AAA BBB C'CC/ --> ('AAA', 'BBB', 'C\'CC')
    my @string = CORE::split(/\s+/, $string);
    for my $string (@string) {
        my @octet = $string =~ /\G ([\x00-\xFF]) /oxmsg;
        for my $octet (@octet) {
            if ($octet =~ /\A (['\\]) \z/oxms) {
                $octet = '\\' . $1;
            }
        }
        $string = join '', @octet;
    }
    return join '', '(', (join ', ', map { "'$_'" } @string), ')';
}

#
# escape here document (<<"HEREDOC", <
#
sub e_heredoc {
    my($string) = @_;

    $slash = 'm//';

    my $metachar = qr/[\@\\|]/oxms; # '|' is for <<`HEREDOC`

    my $left_e  = 0;
    my $right_e = 0;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\$] |
        \\x\{ (?>[0-9A-Fa-f]+) \}            |
        \\o\{ (?>[0-7]+)       \}            |
        \\N\{ (?>[^0-9\}][^\}]*) \} |
        \\ $q_char                           |
        \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  |
        \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     |
                        \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} |
        \$ (?>\s* [0-9]+)                    |
        \$ (?>\s*) \{ (?>\s* [0-9]+ \s*) \}  |
        \$ \$ (?![\w\{])                     |
        \$ (?>\s*) \$ (?>\s*) $qq_variable   |
           $q_char
    ))/oxmsg;

    for (my $i=0; $i <= $#char; $i++) {

        # "\L\u" --> "\u\L"
        if (($char[$i] eq '\L') and ($char[$i+1] eq '\u')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # "\U\l" --> "\l\U"
        elsif (($char[$i] eq '\U') and ($char[$i+1] eq '\l')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::hexchr($1);
        }

        # \N{CHARNAME} --> N{CHARNAME}
        elsif ($char[$i] =~ /\A \\ ( N\{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1;
        }

        if (0) {
        }

        # \u \l \U \L \F \Q \E
        elsif ($char[$i] =~ /\A ([<>]) \z/oxms) {
            if ($right_e < $left_e) {
                $char[$i] = '\\' . $char[$i];
            }
        }
        elsif ($char[$i] eq '\u') {
            $char[$i] = '@{[Ekoi8u::ucfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\l') {
            $char[$i] = '@{[Ekoi8u::lcfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\U') {
            $char[$i] = '@{[Ekoi8u::uc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\L') {
            $char[$i] = '@{[Ekoi8u::lc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\F') {
            $char[$i] = '@{[Ekoi8u::fc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\Q') {
            $char[$i] = '@{[CORE::quotemeta qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\E') {
            if ($right_e < $left_e) {
                $char[$i] = '>]}';
                $right_e++;
            }
            else {
                $char[$i] = '';
            }
        }
        elsif ($char[$i] eq '\Q') {
            while (1) {
                if (++$i > $#char) {
                    last;
                }
                if ($char[$i] eq '\E') {
                    last;
                }
            }
        }
        elsif ($char[$i] eq '\E') {
        }

        # $0 --> $0
        elsif ($char[$i] =~ /\A \$ 0 \z/oxms) {
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) 0 (?>\s*) \} \z/oxms) {
        }

        # $$ --> $$
        elsif ($char[$i] =~ /\A \$\$ \z/oxms) {
        }

        # $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
        # $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($char[$i] =~ /\A \$ ((?>[1-9][0-9]*)) \z/oxms) {
            $char[$i] = e_capture($1);
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
            $char[$i] = e_capture($1);
        }

        # $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ (?:$qq_bracket)*? \] ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
        }

        # $$foo{ ... } --> $ $foo->{ ... }
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ (?:$qq_brace)*? \} ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
        }

        # $$foo
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) \z/oxms) {
            $char[$i] = e_capture($1);
        }

        # $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
        elsif ($char[$i] =~ /\A ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::PREMATCH()]}';
        }

        # $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
        elsif ($char[$i] =~ /\A ( \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::MATCH()]}';
        }

        # $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
        elsif ($char[$i] =~ /\A (                 \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) \z/oxmsgc) {
            $char[$i] = '@{[Ekoi8u::POSTMATCH()]}';
        }

        # ${ foo } --> ${ foo }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ (?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* ) \}                                \z/oxms) {
        }

        # ${ ... }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ( .+ ) \} \z/oxms) {
            $char[$i] = e_capture($1);
        }
    }

    # return string
    if ($left_e > $right_e) {
        return join '', @char, '>]}' x ($left_e - $right_e);
    }
    return     join '', @char;
}

#
# escape regexp (m//, qr//)
#
sub e_qr {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # literal null string pattern
    if ($string eq '') {
        $modifier =~ tr/bB//d;
        $modifier =~ tr/i//d;
        return join '', $ope, $delimiter, $end_delimiter, $modifier;
    }

    # /b /B modifier
    elsif ($modifier =~ tr/bB//d) {

        # choice again delimiter
        if ($delimiter =~ / [\@:] /oxms) {
            my @char = $string =~ /\G ([\x00-\xFF]) /oxmsg;
            my %octet = map {$_ => 1} @char;
            if (not $octet{')'}) {
                $delimiter     = '(';
                $end_delimiter = ')';
            }
            elsif (not $octet{'}'}) {
                $delimiter     = '{';
                $end_delimiter = '}';
            }
            elsif (not $octet{']'}) {
                $delimiter     = '[';
                $end_delimiter = ']';
            }
            elsif (not $octet{'>'}) {
                $delimiter     = '<';
                $end_delimiter = '>';
            }
            else {
                for my $char (qw( ! " $ % & * + - . / = ? ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
                    if (not $octet{$char}) {
                        $delimiter     = $char;
                        $end_delimiter = $char;
                        last;
                    }
                }
            }
        }

        if (($ope =~ /\A m? \z/oxms) and ($delimiter eq '?')) {
            return join '', $ope, $delimiter,        $string,      $matched, $end_delimiter, $modifier;
        }
        else {
            return join '', $ope, $delimiter, '(?:', $string, ')', $matched, $end_delimiter, $modifier;
        }
    }

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;
    my $metachar = qr/[\@\\|[\]{^]/oxms;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\$\@\[\(] |
        \\x   (?>[0-9A-Fa-f]{1,2}) |
        \\    (?>[0-7]{2,3})       |
        \\c   [\x40-\x5F]          |
        \\x\{ (?>[0-9A-Fa-f]+) \}  |
        \\o\{ (?>[0-7]+)       \}  |
        \\[bBNpP]\{ (?>[^0-9\}][^\}]*) \} |
        \\  $q_char                |
        \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  |
        \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     |
                        \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} |
        [\$\@] $qq_variable        |
        \$ (?>\s* [0-9]+)          |
        \$ (?>\s*) \{ (?>\s* [0-9]+ \s*) \}  |
        \$ \$ (?![\w\{])           |
        \$ (?>\s*) \$ (?>\s*) $qq_variable   |
        \[\^                       |
        \[\:   (?>[a-z]+) :\]      |
        \[\:\^ (?>[a-z]+) :\]      |
        \(\?                       |
            $q_char
    ))/oxmsg;

    # choice again delimiter
    if ($delimiter =~ / [\@:] /oxms) {
        my %octet = map {$_ => 1} @char;
        if (not $octet{')'}) {
            $delimiter     = '(';
            $end_delimiter = ')';
        }
        elsif (not $octet{'}'}) {
            $delimiter     = '{';
            $end_delimiter = '}';
        }
        elsif (not $octet{']'}) {
            $delimiter     = '[';
            $end_delimiter = ']';
        }
        elsif (not $octet{'>'}) {
            $delimiter     = '<';
            $end_delimiter = '>';
        }
        else {
            for my $char (qw( ! " $ % & * + - . / = ? ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
                if (not $octet{$char}) {
                    $delimiter     = $char;
                    $end_delimiter = $char;
                    last;
                }
            }
        }
    }

    my $left_e  = 0;
    my $right_e = 0;
    for (my $i=0; $i <= $#char; $i++) {

        # "\L\u" --> "\u\L"
        if (($char[$i] eq '\L') and ($char[$i+1] eq '\u')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # "\U\l" --> "\l\U"
        elsif (($char[$i] eq '\U') and ($char[$i+1] eq '\l')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::hexchr($1);
        }

        # \b{...}      --> b\{...}
        # \B{...}      --> B\{...}
        # \N{CHARNAME} --> N\{CHARNAME}
        # \p{PROPERTY} --> p\{PROPERTY}
        # \P{PROPERTY} --> P\{PROPERTY}
        elsif ($char[$i] =~ /\A \\ ([bBNpP]) ( \{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1 . '\\' . $2;
        }

        # \p, \P, \X --> p, P, X
        elsif ($char[$i] =~ /\A \\ ( [pPX] ) \z/oxms) {
            $char[$i] = $1;
        }

        if (0) {
        }

        # join separated multiple-octet
        elsif ($char[$i] =~ /\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms) {
            if (   ($i+3 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+3]) == 3) and (CORE::eval(sprintf '"%s%s%s%s"', @char[$i..$i+3]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 3;
            }
            elsif (($i+2 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+2]) == 2) and (CORE::eval(sprintf '"%s%s%s"',   @char[$i..$i+2]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 2;
            }
            elsif (($i+1 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, $char[$i+1      ]) == 1) and (CORE::eval(sprintf '"%s%s"',     @char[$i..$i+1]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 1;
            }
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;

            # [] make die "Unmatched [] in regexp ...\n"
            # (and so on)

            if ($char[$i+1] eq ']') {
                $i++;
            }

            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;

            # [^] make die "Unmatched [] in regexp ...\n"
            # (and so on)

            if ($char[$i+1] eq ']') {
                $i++;
            }

            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_not_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # \u \l \U \L \F \Q \E
        elsif ($char[$i] =~ /\A [<>] \z/oxms) {
            if ($right_e < $left_e) {
                $char[$i] = '\\' . $char[$i];
            }
        }
        elsif ($char[$i] eq '\u') {
            $char[$i] = '@{[Ekoi8u::ucfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\l') {
            $char[$i] = '@{[Ekoi8u::lcfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\U') {
            $char[$i] = '@{[Ekoi8u::uc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\L') {
            $char[$i] = '@{[Ekoi8u::lc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\F') {
            $char[$i] = '@{[Ekoi8u::fc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\Q') {
            $char[$i] = '@{[CORE::quotemeta qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\E') {
            if ($right_e < $left_e) {
                $char[$i] = '>]}';
                $right_e++;
            }
            else {
                $char[$i] = '';
            }
        }
        elsif ($char[$i] eq '\Q') {
            while (1) {
                if (++$i > $#char) {
                    last;
                }
                if ($char[$i] eq '\E') {
                    last;
                }
            }
        }
        elsif ($char[$i] eq '\E') {
        }

        # $0 --> $0
        elsif ($char[$i] =~ /\A \$ 0 \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) 0 (?>\s*) \} \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$ --> $$
        elsif ($char[$i] =~ /\A \$\$ \z/oxms) {
        }

        # $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
        # $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($char[$i] =~ /\A \$ ((?>[1-9][0-9]*)) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ (?:$qq_bracket)*? \] ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo{ ... } --> $ $foo->{ ... }
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ (?:$qq_brace)*? \} ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
        elsif ($char[$i] =~ /\A ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::PREMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::PREMATCH()]}';
            }
        }

        # $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
        elsif ($char[$i] =~ /\A ( \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::MATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::MATCH()]}';
            }
        }

        # $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
        elsif ($char[$i] =~ /\A (                 \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::POSTMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::POSTMATCH()]}';
            }
        }

        # ${ foo }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ((?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* )) \}                              \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # ${ ... }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ( .+ ) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $scalar or @array
        elsif ($char[$i] =~ /\A [\$\@].+ /oxms) {
            $char[$i] = e_string($char[$i]);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A (?:[\x00-\xFF]|\\[0-7]{2,3}|\\x[0-9-A-Fa-f]{1,2}) \z/oxms) {
            }
            elsif (($ope =~ /\A m? \z/oxms) and ($delimiter eq '?')) {
                my $char = $char[$i-1];
                if ($char[$i] eq '{') {
                    die __FILE__, qq{: "MULTIBYTE{n}" should be "(MULTIBYTE){n}" in m?? (and shift \$1,\$2,\$3,...) ($char){n}\n};
                }
                else {
                    die __FILE__, qq{: "MULTIBYTE$char[$i]" should be "(MULTIBYTE)$char[$i]" in m?? (and shift \$1,\$2,\$3,...) ($char)$char[$i]\n};
                }
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    # make regexp string
    $modifier =~ tr/i//d;
    if ($left_e > $right_e) {
        if (($ope =~ /\A m? \z/oxms) and ($delimiter eq '?')) {
            return join '', $ope, $delimiter, $anchor,        @char, '>]}' x ($left_e - $right_e),      $matched, $end_delimiter, $modifier;
        }
        else {
            return join '', $ope, $delimiter, $anchor, '(?:', @char, '>]}' x ($left_e - $right_e), ')', $matched, $end_delimiter, $modifier;
        }
    }
    if (($ope =~ /\A m? \z/oxms) and ($delimiter eq '?')) {
        return     join '', $ope, $delimiter, $anchor,        @char,                                    $matched, $end_delimiter, $modifier;
    }
    else {
        return     join '', $ope, $delimiter, $anchor, '(?:', @char,                               ')', $matched, $end_delimiter, $modifier;
    }
}

#
# double quote stuff
#
sub qq_stuff {
    my($delimiter,$end_delimiter,$stuff) = @_;

    # scalar variable or array variable
    if ($stuff =~ /\A [\$\@] /oxms) {
        return $stuff;
    }

    # quote by delimiter
    my %octet = map {$_ => 1} ($stuff =~ /\G ([\x00-\xFF]) /oxmsg);
    for my $char (qw( ! " $ % & * + - . / : = ? @ ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
        next if $char eq $delimiter;
        next if $char eq $end_delimiter;
        if (not $octet{$char}) {
            return join '', 'qq', $char, $stuff, $char;
        }
    }
    return join '', 'qq', '<', $stuff, '>';
}

#
# escape regexp (m'', qr'', and m''b, qr''b)
#
sub e_qr_q {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # literal null string pattern
    if ($string eq '') {
        $modifier =~ tr/bB//d;
        $modifier =~ tr/i//d;
        return join '', $ope, $delimiter, $end_delimiter, $modifier;
    }

    # with /b /B modifier
    elsif ($modifier =~ tr/bB//d) {
        return e_qr_qb($ope,$delimiter,$end_delimiter,$string,$modifier);
    }

    # without /b /B modifier
    else {
        return e_qr_qt($ope,$delimiter,$end_delimiter,$string,$modifier);
    }
}

#
# escape regexp (m'', qr'')
#
sub e_qr_qt {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\[\$\@\/] |
        [\x00-\xFF] |
        \[\^                            |
        \[\:   (?>[a-z]+) \:\]          |
        \[\:\^ (?>[a-z]+) \:\]          |
        [\$\@\/]                        |
        \\     (?:$q_char)              |
               (?:$q_char)
    ))/oxmsg;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # escape $ @ / and \
        elsif ($char[$i] =~ /\A [\$\@\/\\] \z/oxms) {
            $char[$i] = '\\' . $char[$i];
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A [\x00-\xFF] \z/oxms) {
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    $delimiter     = '/';
    $end_delimiter = '/';

    $modifier =~ tr/i//d;
    return join '', $ope, $delimiter, $anchor, '(?:', @char, ')', $matched, $end_delimiter, $modifier;
}

#
# escape regexp (m''b, qr''b)
#
sub e_qr_qb {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;

    # split regexp
    my @char = $string =~ /\G ((?>[^\\]|\\\\)) /oxmsg;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # remain \\
        elsif ($char[$i] eq '\\\\') {
        }

        # escape $ @ / and \
        elsif ($char[$i] =~ /\A [\$\@\/\\] \z/oxms) {
            $char[$i] = '\\' . $char[$i];
        }
    }

    $delimiter     = '/';
    $end_delimiter = '/';
    return join '', $ope, $delimiter, '(?:', @char, ')', $matched, $end_delimiter, $modifier;
}

#
# escape regexp (s/here//)
#
sub e_s1 {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # literal null string pattern
    if ($string eq '') {
        $modifier =~ tr/bB//d;
        $modifier =~ tr/i//d;
        return join '', $ope, $delimiter, $end_delimiter, $modifier;
    }

    # /b /B modifier
    elsif ($modifier =~ tr/bB//d) {

        # choice again delimiter
        if ($delimiter =~ / [\@:] /oxms) {
            my @char = $string =~ /\G ([\x00-\xFF]) /oxmsg;
            my %octet = map {$_ => 1} @char;
            if (not $octet{')'}) {
                $delimiter     = '(';
                $end_delimiter = ')';
            }
            elsif (not $octet{'}'}) {
                $delimiter     = '{';
                $end_delimiter = '}';
            }
            elsif (not $octet{']'}) {
                $delimiter     = '[';
                $end_delimiter = ']';
            }
            elsif (not $octet{'>'}) {
                $delimiter     = '<';
                $end_delimiter = '>';
            }
            else {
                for my $char (qw( ! " $ % & * + - . / = ? ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
                    if (not $octet{$char}) {
                        $delimiter     = $char;
                        $end_delimiter = $char;
                        last;
                    }
                }
            }
        }

        my $prematch = '';
        return join '', $ope, $delimiter, $prematch, '(?:', $string, ')', $matched, $end_delimiter, $modifier;
    }

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;
    my $metachar = qr/[\@\\|[\]{^]/oxms;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\$\@\[\(] |
        \\                               (?>[1-9][0-9]*)            |
        \\g (?>\s*)                      (?>[1-9][0-9]*)            |
        \\g (?>\s*) \{ (?>\s*)           (?>[1-9][0-9]*) (?>\s*) \} |
        \\g (?>\s*) \{ (?>\s*) - (?>\s*) (?>[1-9][0-9]*) (?>\s*) \} |
        \\x                              (?>[0-9A-Fa-f]{1,2})       |
        \\                               (?>[0-7]{2,3})             |
        \\c                              [\x40-\x5F]                |
        \\x\{                            (?>[0-9A-Fa-f]+)        \} |
        \\o\{                            (?>[0-7]+)              \} |
        \\[bBNpP]\{                      (?>[^0-9\}][^\}]*) \} |
        \\ $q_char                           |
        \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  |
        \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     |
                        \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} |
        [\$\@] $qq_variable                  |
        \$ (?>\s* [0-9]+)                    |
        \$ (?>\s*) \{ (?>\s* [0-9]+ \s*) \}  |
        \$ \$ (?![\w\{])                     |
        \$ (?>\s*) \$ (?>\s*) $qq_variable   |
        \[\^                                 |
        \[\:   (?>[a-z]+) :\]                |
        \[\:\^ (?>[a-z]+) :\]                |
        \(\?                                 |
            $q_char
    ))/oxmsg;

    # choice again delimiter
    if ($delimiter =~ / [\@:] /oxms) {
        my %octet = map {$_ => 1} @char;
        if (not $octet{')'}) {
            $delimiter     = '(';
            $end_delimiter = ')';
        }
        elsif (not $octet{'}'}) {
            $delimiter     = '{';
            $end_delimiter = '}';
        }
        elsif (not $octet{']'}) {
            $delimiter     = '[';
            $end_delimiter = ']';
        }
        elsif (not $octet{'>'}) {
            $delimiter     = '<';
            $end_delimiter = '>';
        }
        else {
            for my $char (qw( ! " $ % & * + - . / = ? ^ ` | ~ ), "\x00".."\x1F", "\x7F", "\xFF") {
                if (not $octet{$char}) {
                    $delimiter     = $char;
                    $end_delimiter = $char;
                    last;
                }
            }
        }
    }

    # count '('
    my $parens = grep { $_ eq '(' } @char;

    my $left_e  = 0;
    my $right_e = 0;
    for (my $i=0; $i <= $#char; $i++) {

        # "\L\u" --> "\u\L"
        if (($char[$i] eq '\L') and ($char[$i+1] eq '\u')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # "\U\l" --> "\l\U"
        elsif (($char[$i] eq '\U') and ($char[$i+1] eq '\l')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::hexchr($1);
        }

        # \b{...}      --> b\{...}
        # \B{...}      --> B\{...}
        # \N{CHARNAME} --> N\{CHARNAME}
        # \p{PROPERTY} --> p\{PROPERTY}
        # \P{PROPERTY} --> P\{PROPERTY}
        elsif ($char[$i] =~ /\A \\ ([bBNpP]) ( \{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1 . '\\' . $2;
        }

        # \p, \P, \X --> p, P, X
        elsif ($char[$i] =~ /\A \\ ( [pPX] ) \z/oxms) {
            $char[$i] = $1;
        }

        if (0) {
        }

        # join separated multiple-octet
        elsif ($char[$i] =~ /\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms) {
            if (   ($i+3 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+3]) == 3) and (CORE::eval(sprintf '"%s%s%s%s"', @char[$i..$i+3]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 3;
            }
            elsif (($i+2 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+2]) == 2) and (CORE::eval(sprintf '"%s%s%s"',   @char[$i..$i+2]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 2;
            }
            elsif (($i+1 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, $char[$i+1      ]) == 1) and (CORE::eval(sprintf '"%s%s"',     @char[$i..$i+1]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 1;
            }
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_not_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # \u \l \U \L \F \Q \E
        elsif ($char[$i] =~ /\A [<>] \z/oxms) {
            if ($right_e < $left_e) {
                $char[$i] = '\\' . $char[$i];
            }
        }
        elsif ($char[$i] eq '\u') {
            $char[$i] = '@{[Ekoi8u::ucfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\l') {
            $char[$i] = '@{[Ekoi8u::lcfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\U') {
            $char[$i] = '@{[Ekoi8u::uc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\L') {
            $char[$i] = '@{[Ekoi8u::lc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\F') {
            $char[$i] = '@{[Ekoi8u::fc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\Q') {
            $char[$i] = '@{[CORE::quotemeta qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\E') {
            if ($right_e < $left_e) {
                $char[$i] = '>]}';
                $right_e++;
            }
            else {
                $char[$i] = '';
            }
        }
        elsif ($char[$i] eq '\Q') {
            while (1) {
                if (++$i > $#char) {
                    last;
                }
                if ($char[$i] eq '\E') {
                    last;
                }
            }
        }
        elsif ($char[$i] eq '\E') {
        }

        # \0 --> \0
        elsif ($char[$i] =~ /\A \\ (?>\s*) 0 \z/oxms) {
        }

        # \g{N}, \g{-N}

        # P.108 Using Simple Patterns
        # in Chapter 7: In the World of Regular Expressions
        # of ISBN 978-0-596-52010-6 Learning Perl, Fifth Edition

        # P.221 Capturing
        # in Chapter 5: Pattern Matching
        # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

        # \g{-1}, \g{-2}, \g{-3} --> \g{-1}, \g{-2}, \g{-3}
        elsif ($char[$i] =~ /\A \\g (?>\s*) \{ (?>\s*) - (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
        }

        # \g{1}, \g{2}, \g{3} --> \g{2}, \g{3}, \g{4} (only when multibyte anchoring is enable)
        elsif ($char[$i] =~ /\A \\g (?>\s*) \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
        }

        # \g1, \g2, \g3 --> \g2, \g3, \g4 (only when multibyte anchoring is enable)
        elsif ($char[$i] =~ /\A \\g (?>\s*) ((?>[1-9][0-9]*)) \z/oxms) {
        }

        # \1, \2, \3 --> \2, \3, \4 (only when multibyte anchoring is enable)
        elsif ($char[$i] =~ /\A \\ (?>\s*) ((?>[1-9][0-9]*)) \z/oxms) {
        }

        # $0 --> $0
        elsif ($char[$i] =~ /\A \$ 0 \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) 0 (?>\s*) \} \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$ --> $$
        elsif ($char[$i] =~ /\A \$\$ \z/oxms) {
        }

        # $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
        # $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($char[$i] =~ /\A \$ ((?>[1-9][0-9]*)) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ (?:$qq_bracket)*? \] ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo{ ... } --> $ $foo->{ ... }
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ (?:$qq_brace)*? \} ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
        elsif ($char[$i] =~ /\A ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::PREMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::PREMATCH()]}';
            }
        }

        # $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
        elsif ($char[$i] =~ /\A ( \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::MATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::MATCH()]}';
            }
        }

        # $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
        elsif ($char[$i] =~ /\A (                 \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::POSTMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::POSTMATCH()]}';
            }
        }

        # ${ foo }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ((?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* )) \}                              \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # ${ ... }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ( .+ ) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $scalar or @array
        elsif ($char[$i] =~ /\A [\$\@].+ /oxms) {
            $char[$i] = e_string($char[$i]);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A (?:[\x00-\xFF]|\\[0-7]{2,3}|\\x[0-9-A-Fa-f]{1,2}) \z/oxms) {
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    # make regexp string
    my $prematch = '';
    $modifier =~ tr/i//d;
    if ($left_e > $right_e) {
        return join '', $ope, $delimiter, $prematch, '(?:', @char, '>]}' x ($left_e - $right_e), ')', $matched, $end_delimiter, $modifier;
    }
    return     join '', $ope, $delimiter, $prematch, '(?:', @char,                               ')', $matched, $end_delimiter, $modifier;
}

#
# escape regexp (s'here'' or s'here''b)
#
sub e_s1_q {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # literal null string pattern
    if ($string eq '') {
        $modifier =~ tr/bB//d;
        $modifier =~ tr/i//d;
        return join '', $ope, $delimiter, $end_delimiter, $modifier;
    }

    # with /b /B modifier
    elsif ($modifier =~ tr/bB//d) {
        return e_s1_qb($ope,$delimiter,$end_delimiter,$string,$modifier);
    }

    # without /b /B modifier
    else {
        return e_s1_qt($ope,$delimiter,$end_delimiter,$string,$modifier);
    }
}

#
# escape regexp (s'here'')
#
sub e_s1_qt {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\[\$\@\/] |
        [\x00-\xFF] |
        \[\^                            |
        \[\:   (?>[a-z]+) \:\]          |
        \[\:\^ (?>[a-z]+) \:\]          |
        [\$\@\/]                        |
        \\     (?:$q_char)              |
               (?:$q_char)
    ))/oxmsg;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # escape $ @ / and \
        elsif ($char[$i] =~ /\A [\$\@\/\\] \z/oxms) {
            $char[$i] = '\\' . $char[$i];
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A [\x00-\xFF] \z/oxms) {
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    $modifier =~ tr/i//d;
    $delimiter     = '/';
    $end_delimiter = '/';
    my $prematch = '';
    return join '', $ope, $delimiter, $prematch, '(?:', @char, ')', $matched, $end_delimiter, $modifier;
}

#
# escape regexp (s'here''b)
#
sub e_s1_qb {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;

    # split regexp
    my @char = $string =~ /\G (?>[^\\]|\\\\) /oxmsg;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # remain \\
        elsif ($char[$i] eq '\\\\') {
        }

        # escape $ @ / and \
        elsif ($char[$i] =~ /\A [\$\@\/\\] \z/oxms) {
            $char[$i] = '\\' . $char[$i];
        }
    }

    $delimiter     = '/';
    $end_delimiter = '/';
    my $prematch = '';
    return join '', $ope, $delimiter, $prematch, '(?:', @char, ')', $matched, $end_delimiter, $modifier;
}

#
# escape regexp (s''here')
#
sub e_s2_q {
    my($ope,$delimiter,$end_delimiter,$string) = @_;

    $slash = 'div';

    my @char = $string =~ / \G (?>[^\\]|\\\\|$q_char) /oxmsg;
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # not escape \\
        elsif ($char[$i] =~ /\A \\\\ \z/oxms) {
        }

        # escape $ @ / and \
        elsif ($char[$i] =~ /\A [\$\@\/\\] \z/oxms) {
            $char[$i] = '\\' . $char[$i];
        }
    }

    return join '', $ope, $delimiter, @char,   $end_delimiter;
}

#
# escape regexp (s/here/and here/modifier)
#
sub e_sub {
    my($variable,$delimiter1,$pattern,$end_delimiter1,$delimiter2,$replacement,$end_delimiter2,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    if ($variable eq '') {
        $variable      = '$_';
        $bind_operator = ' =~ ';
    }

    $slash = 'div';

    # P.128 Start of match (or end of previous match): \G
    # P.130 Advanced Use of \G with Perl
    # in Chapter 3: Overview of Regular Expression Features and Flavors
    # P.312 Iterative Matching: Scalar Context, with /g
    # in Chapter 7: Perl
    # of ISBN 0-596-00289-0 Mastering Regular Expressions, Second edition

    # P.181 Where You Left Off: The \G Assertion
    # in Chapter 5: Pattern Matching
    # of ISBN 0-596-00027-8 Programming Perl Third Edition.

    # P.220 Where You Left Off: The \G Assertion
    # in Chapter 5: Pattern Matching
    # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

    my $e_modifier = $modifier =~ tr/e//d;
    my $r_modifier = $modifier =~ tr/r//d;

    my $my = '';
    if ($variable =~ s/\A \( (?>\s*) ( (?>(?: local \b | my \b | our \b | state \b )?) .+ ) \) \z/$1/oxms) {
        $my = $variable;
        $variable =~ s/ (?: local \b | my \b | our \b | state \b ) (?>\s*) //oxms;
        $variable =~ s/ = .+ \z//oxms;
    }

    (my $variable_basename = $variable) =~ s/ [\[\{].* \z//oxms;
    $variable_basename =~ s/ \s+ \z//oxms;

    # quote replacement string
    my $e_replacement = '';
    if ($e_modifier >= 1) {
        $e_replacement = e_qq('', '', '', $replacement);
        $e_modifier--;
    }
    else {
        if ($delimiter2 eq "'") {
            $e_replacement = e_s2_q('qq', '/',         '/',             $replacement);
        }
        else {
            $e_replacement = e_qq  ('qq', $delimiter2, $end_delimiter2, $replacement);
        }
    }

    my $sub = '';

    # with /r
    if ($r_modifier) {
        if (0) {
        }

        # s///gr without multibyte anchoring
        elsif ($modifier =~ /g/oxms) {
            $sub = sprintf(
                #                               1                         2   3                                  4   5
                q,

                $variable,                                                       #  1
                ($delimiter1 eq "'") ?                                           #  2
                e_s1_q('m', $delimiter1, $end_delimiter1, $pattern, $modifier) : #  :
                e_s1  ('m', $delimiter1, $end_delimiter1, $pattern, $modifier),  #  :
                $s_matched,                                                      #  3
                $e_replacement,                                                  #  4
                '$Ekoi8u::re_r=CORE::eval $Ekoi8u::re_r; ' x $e_modifier,          #  5
            );
        }

        # s///r
        else {

            my $prematch = q{$`};

            $sub = sprintf(
                #  1     2                3                                  4   5  6                     7
                q<(%s =~ %s) ? CORE::eval{%s local $^W=0; local $Ekoi8u::re_r=%s; %s"%s$Ekoi8u::re_r$'" } : %s>,

                $variable,                                                       #  1
                ($delimiter1 eq "'") ?                                           #  2
                e_s1_q('m', $delimiter1, $end_delimiter1, $pattern, $modifier) : #  :
                e_s1  ('m', $delimiter1, $end_delimiter1, $pattern, $modifier),  #  :
                $s_matched,                                                      #  3
                $e_replacement,                                                  #  4
                '$Ekoi8u::re_r=CORE::eval $Ekoi8u::re_r; ' x $e_modifier,          #  5
                $prematch,                                                       #  6
                $variable,                                                       #  7
            );
        }

        # $var !~ s///r doesn't make sense
        if ($bind_operator =~ / !~ /oxms) {
            $sub = q{die("$0: Using !~ with s///r doesn't make sense"), } . $sub;
        }
    }

    # without /r
    else {
        if (0) {
        }

        # s///g without multibyte anchoring
        elsif ($modifier =~ /g/oxms) {
            $sub = sprintf(
                #                                        1     2   3                                  4   5 6                          7                                                   8
                q,

                $variable,                                                       #  1
                ($delimiter1 eq "'") ?                                           #  2
                e_s1_q('m', $delimiter1, $end_delimiter1, $pattern, $modifier) : #  :
                e_s1  ('m', $delimiter1, $end_delimiter1, $pattern, $modifier),  #  :
                $s_matched,                                                      #  3
                $e_replacement,                                                  #  4
                '$Ekoi8u::re_r=CORE::eval $Ekoi8u::re_r; ' x $e_modifier,          #  5
                $variable,                                                       #  6
                $variable,                                                       #  7
                ($bind_operator =~ / !~ /oxms) ? '!' : '',                       #  8
            );
        }

        # s///
        else {

            my $prematch = q{$`};

            $sub = sprintf(

                ($bind_operator =~ / =~ /oxms) ?

                #  1 2 3                4                                  5   6 7   8
                q<(%s%s%s) ? CORE::eval{%s local $^W=0; local $Ekoi8u::re_r=%s; %s%s="%s$Ekoi8u::re_r$'"; 1 } : undef> :

                #  1 2 3                    4                                  5   6 7   8
                q<(%s%s%s) ? 1 : CORE::eval{%s local $^W=0; local $Ekoi8u::re_r=%s; %s%s="%s$Ekoi8u::re_r$'"; undef }>,

                $variable,                                                       #  1
                $bind_operator,                                                  #  2
                ($delimiter1 eq "'") ?                                           #  3
                e_s1_q('m', $delimiter1, $end_delimiter1, $pattern, $modifier) : #  :
                e_s1  ('m', $delimiter1, $end_delimiter1, $pattern, $modifier),  #  :
                $s_matched,                                                      #  4
                $e_replacement,                                                  #  5
                '$Ekoi8u::re_r=CORE::eval $Ekoi8u::re_r; ' x $e_modifier,          #  6
                $variable,                                                       #  7
                $prematch,                                                       #  8
            );
        }
    }

    # (my $foo = $bar) =~ s///   -->   (my $foo = $bar, CORE::eval { ... })[1]
    if ($my ne '') {
        $sub = "($my, $sub)[1]";
    }

    # clear s/// variable
    $sub_variable = '';
    $bind_operator = '';

    return $sub;
}

#
# escape regexp of split qr//
#
sub e_split {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # /b /B modifier
    if ($modifier =~ tr/bB//d) {
        return join '', 'split', $ope, $delimiter, $string, $end_delimiter, $modifier;
    }

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;
    my $metachar = qr/[\@\\|[\]{^]/oxms;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\$\@\[\(] |
        \\x   (?>[0-9A-Fa-f]{1,2}) |
        \\    (?>[0-7]{2,3})       |
        \\c   [\x40-\x5F]          |
        \\x\{ (?>[0-9A-Fa-f]+) \}  |
        \\o\{ (?>[0-7]+)       \}  |
        \\[bBNpP]\{ (?>[^0-9\}][^\}]*) \} |
        \\  $q_char                |
        \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  |
        \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     |
                        \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} |
        [\$\@] $qq_variable        |
        \$ (?>\s* [0-9]+)          |
        \$ (?>\s*) \{ (?>\s* [0-9]+ \s*) \}  |
        \$ \$ (?![\w\{])           |
        \$ (?>\s*) \$ (?>\s*) $qq_variable   |
        \[\^                       |
        \[\:   (?>[a-z]+) :\]      |
        \[\:\^ (?>[a-z]+) :\]      |
        \(\?                       |
            $q_char
    ))/oxmsg;

    my $left_e  = 0;
    my $right_e = 0;
    for (my $i=0; $i <= $#char; $i++) {

        # "\L\u" --> "\u\L"
        if (($char[$i] eq '\L') and ($char[$i+1] eq '\u')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # "\U\l" --> "\l\U"
        elsif (($char[$i] eq '\U') and ($char[$i+1] eq '\l')) {
            @char[$i,$i+1] = @char[$i+1,$i];
        }

        # octal escape sequence
        elsif ($char[$i] =~ /\A \\o \{ ([0-7]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::octchr($1);
        }

        # hexadecimal escape sequence
        elsif ($char[$i] =~ /\A \\x \{ ([0-9A-Fa-f]+) \} \z/oxms) {
            $char[$i] = Ekoi8u::hexchr($1);
        }

        # \b{...}      --> b\{...}
        # \B{...}      --> B\{...}
        # \N{CHARNAME} --> N\{CHARNAME}
        # \p{PROPERTY} --> p\{PROPERTY}
        # \P{PROPERTY} --> P\{PROPERTY}
        elsif ($char[$i] =~ /\A \\ ([bBNpP]) ( \{ ([^0-9\}][^\}]*) \} ) \z/oxms) {
            $char[$i] = $1 . '\\' . $2;
        }

        # \p, \P, \X --> p, P, X
        elsif ($char[$i] =~ /\A \\ ( [pPX] ) \z/oxms) {
            $char[$i] = $1;
        }

        if (0) {
        }

        # join separated multiple-octet
        elsif ($char[$i] =~ /\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms) {
            if (   ($i+3 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+3]) == 3) and (CORE::eval(sprintf '"%s%s%s%s"', @char[$i..$i+3]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 3;
            }
            elsif (($i+2 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, @char[$i+1..$i+2]) == 2) and (CORE::eval(sprintf '"%s%s%s"',   @char[$i..$i+2]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 2;
            }
            elsif (($i+1 <= $#char) and (grep(/\A (?: \\ [0-7]{2,3} | \\x [0-9A-Fa-f]{1,2}) \z/oxms, $char[$i+1      ]) == 1) and (CORE::eval(sprintf '"%s%s"',     @char[$i..$i+1]) =~ /\A $q_char \z/oxms)) {
                $char[$i] .= join '', splice @char, $i+1, 1;
            }
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    if (grep(/\A [\$\@]/oxms,@char[$left+1..$right-1]) >= 1) {
                        splice @char, $left, $right-$left+1, sprintf(q{@{[Ekoi8u::charlist_not_qr(%s,'%s')]}}, join(',', map {qq_stuff($delimiter,$end_delimiter,$_)} @char[$left+1..$right-1]), $modifier);
                    }
                    else {
                        splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);
                    }

                    $i = $left;
                    last;
                }
            }
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # P.794 29.2.161. split
        # in Chapter 29: Functions
        # of ISBN 0-596-00027-8 Programming Perl Third Edition.

        # P.951 split
        # in Chapter 27: Functions
        # of ISBN 978-0-596-00492-7 Programming Perl 4th Edition.

        # said "The //m modifier is assumed when you split on the pattern /^/",
        # but perl5.008 is not so. Therefore, this software adds //m.
        # (and so on)

        # split(m/^/) --> split(m/^/m)
        elsif (($char[$i] eq '^') and ($modifier !~ /m/oxms)) {
            $modifier .= 'm';
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # \u \l \U \L \F \Q \E
        elsif ($char[$i] =~ /\A ([<>]) \z/oxms) {
            if ($right_e < $left_e) {
                $char[$i] = '\\' . $char[$i];
            }
        }
        elsif ($char[$i] eq '\u') {
            $char[$i] = '@{[Ekoi8u::ucfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\l') {
            $char[$i] = '@{[Ekoi8u::lcfirst qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\U') {
            $char[$i] = '@{[Ekoi8u::uc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\L') {
            $char[$i] = '@{[Ekoi8u::lc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\F') {
            $char[$i] = '@{[Ekoi8u::fc qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\Q') {
            $char[$i] = '@{[CORE::quotemeta qq<';
            $left_e++;
        }
        elsif ($char[$i] eq '\E') {
            if ($right_e < $left_e) {
                $char[$i] = '>]}';
                $right_e++;
            }
            else {
                $char[$i] = '';
            }
        }
        elsif ($char[$i] eq '\Q') {
            while (1) {
                if (++$i > $#char) {
                    last;
                }
                if ($char[$i] eq '\E') {
                    last;
                }
            }
        }
        elsif ($char[$i] eq '\E') {
        }

        # $0 --> $0
        elsif ($char[$i] =~ /\A \$ 0 \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) 0 (?>\s*) \} \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$ --> $$
        elsif ($char[$i] =~ /\A \$\$ \z/oxms) {
        }

        # $1, $2, $3 --> $2, $3, $4 after s/// with multibyte anchoring
        # $1, $2, $3 --> $1, $2, $3 otherwise
        elsif ($char[$i] =~ /\A \$ ((?>[1-9][0-9]*)) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }
        elsif ($char[$i] =~ /\A \$ \{ (?>\s*) ((?>[1-9][0-9]*)) (?>\s*) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo[ ... ] --> $ $foo->[ ... ]
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \[ (?:$qq_bracket)*? \] ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo{ ... } --> $ $foo->{ ... }
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) ( \{ (?:$qq_brace)*? \} ) \z/oxms) {
            $char[$i] = e_capture($1.'->'.$2);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $$foo
        elsif ($char[$i] =~ /\A \$ ((?> \$ [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* )) \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $`, ${`}, $PREMATCH, ${PREMATCH}, ${^PREMATCH} --> Ekoi8u::PREMATCH()
        elsif ($char[$i] =~ /\A ( \$` | \$\{`\} | \$ (?>\s*) PREMATCH  | \$ (?>\s*) \{ (?>\s*) PREMATCH  (?>\s*) \} | \$ (?>\s*) \{\^PREMATCH\}  ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::PREMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::PREMATCH()]}';
            }
        }

        # $&, ${&}, $MATCH, ${MATCH}, ${^MATCH} --> Ekoi8u::MATCH()
        elsif ($char[$i] =~ /\A ( \$& | \$\{&\} | \$ (?>\s*) MATCH     | \$ (?>\s*) \{ (?>\s*) MATCH     (?>\s*) \} | \$ (?>\s*) \{\^MATCH\}     ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::MATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::MATCH()]}';
            }
        }

        # $POSTMATCH, ${POSTMATCH}, ${^POSTMATCH} --> Ekoi8u::POSTMATCH()
        elsif ($char[$i] =~ /\A (                 \$ (?>\s*) POSTMATCH | \$ (?>\s*) \{ (?>\s*) POSTMATCH (?>\s*) \} | \$ (?>\s*) \{\^POSTMATCH\} ) \z/oxmsgc) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(Ekoi8u::POSTMATCH())]}';
            }
            else {
                $char[$i] = '@{[Ekoi8u::POSTMATCH()]}';
            }
        }

        # ${ foo }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ((?> \s* [A-Za-z_][A-Za-z0-9_]*(?: ::[A-Za-z_][A-Za-z0-9_]*)* \s* )) \}                            \z/oxms) {
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $1 . ')]}';
            }
        }

        # ${ ... }
        elsif ($char[$i] =~ /\A \$ (?>\s*) \{ ( .+ ) \} \z/oxms) {
            $char[$i] = e_capture($1);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # $scalar or @array
        elsif ($char[$i] =~ /\A [\$\@].+ /oxms) {
            $char[$i] = e_string($char[$i]);
            if ($ignorecase) {
                $char[$i] = '@{[Ekoi8u::ignorecase(' . $char[$i] . ')]}';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A (?:[\x00-\xFF]|\\[0-7]{2,3}|\\x[0-9-A-Fa-f]{1,2}) \z/oxms) {
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    # make regexp string
    $modifier =~ tr/i//d;
    if ($left_e > $right_e) {
        return join '', 'Ekoi8u::split', $ope, $delimiter, @char, '>]}' x ($left_e - $right_e), $end_delimiter, $modifier;
    }
    return     join '', 'Ekoi8u::split', $ope, $delimiter, @char,                               $end_delimiter, $modifier;
}

#
# escape regexp of split qr''
#
sub e_split_q {
    my($ope,$delimiter,$end_delimiter,$string,$modifier) = @_;
    $modifier ||= '';

    $modifier =~ tr/p//d;
    if ($modifier =~ /([adlu])/oxms) {
        my $line = 0;
        for (my $i=0; my($package,$filename,$use_line,$subroutine) = caller($i); $i++) {
            if ($filename ne __FILE__) {
                $line = $use_line + (CORE::substr($_,0,pos($_)) =~ tr/\n//) + 1;
                last;
            }
        }
        die qq{Unsupported modifier "$1" used at line $line.\n};
    }

    $slash = 'div';

    # /b /B modifier
    if ($modifier =~ tr/bB//d) {
        return join '', 'split', $ope, $delimiter, $string, $end_delimiter, $modifier;
    }

    my $ignorecase = ($modifier =~ /i/oxms) ? 1 : 0;

    # split regexp
    my @char = $string =~ /\G((?>
        [^\\\[]       |
        [\x00-\xFF] |
        \[\^                            |
        \[\:   (?>[a-z]+) \:\]          |
        \[\:\^ (?>[a-z]+) \:\]          |
        \\     (?:$q_char)              |
               (?:$q_char)
    ))/oxmsg;

    # unescape character
    for (my $i=0; $i <= $#char; $i++) {
        if (0) {
        }

        # open character class [...]
        elsif ($char[$i] eq '[') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # open character class [^...]
        elsif ($char[$i] eq '[^') {
            my $left = $i;
            if ($char[$i+1] eq ']') {
                $i++;
            }
            while (1) {
                if (++$i > $#char) {
                    die __FILE__, ": Unmatched [] in regexp\n";
                }
                if ($char[$i] eq ']') {
                    my $right = $i;

                    # [^...]
                    splice @char, $left, $right-$left+1, Ekoi8u::charlist_not_qr(@char[$left+1..$right-1], $modifier);

                    $i = $left;
                    last;
                }
            }
        }

        # rewrite character class or escape character
        elsif (my $char = character_class($char[$i],$modifier)) {
            $char[$i] = $char;
        }

        # split(m/^/) --> split(m/^/m)
        elsif (($char[$i] eq '^') and ($modifier !~ /m/oxms)) {
            $modifier .= 'm';
        }

        # /i modifier
        elsif ($ignorecase and ($char[$i] =~ /\A [\x00-\xFF] \z/oxms) and (Ekoi8u::uc($char[$i]) ne Ekoi8u::fc($char[$i]))) {
            if (CORE::length(Ekoi8u::fc($char[$i])) == 1) {
                $char[$i] = '['   . Ekoi8u::uc($char[$i])       . Ekoi8u::fc($char[$i]) . ']';
            }
            else {
                $char[$i] = '(?:' . Ekoi8u::uc($char[$i]) . '|' . Ekoi8u::fc($char[$i]) . ')';
            }
        }

        # quote character before ? + * {
        elsif (($i >= 1) and ($char[$i] =~ /\A [\?\+\*\{] \z/oxms)) {
            if ($char[$i-1] =~ /\A [\x00-\xFF] \z/oxms) {
            }
            else {
                $char[$i-1] = '(?:' . $char[$i-1] . ')';
            }
        }
    }

    $modifier =~ tr/i//d;
    return join '', 'Ekoi8u::split', $ope, $delimiter, @char, $end_delimiter, $modifier;
}

#
# instead of Carp::carp
#
sub carp {
    my($package,$filename,$line) = caller(1);
    print STDERR "@_ at $filename line $line.\n";
}

#
# instead of Carp::croak
#
sub croak {
    my($package,$filename,$line) = caller(1);
    print STDERR "@_ at $filename line $line.\n";
    die "\n";
}

#
# instead of Carp::cluck
#
sub cluck {
    my $i = 0;
    my @cluck = ();
    while (my($package,$filename,$line,$subroutine) = caller($i)) {
        push @cluck, "[$i] $filename($line) $package::$subroutine\n";
        $i++;
    }
    print STDERR CORE::reverse @cluck;
    print STDERR "\n";
    print STDERR @_;
}

#
# instead of Carp::confess
#
sub confess {
    my $i = 0;
    my @confess = ();
    while (my($package,$filename,$line,$subroutine) = caller($i)) {
        push @confess, "[$i] $filename($line) $package::$subroutine\n";
        $i++;
    }
    print STDERR CORE::reverse @confess;
    print STDERR "\n";
    print STDERR @_;
    die "\n";
}

1;

__END__