package Encode::ROT13;

use strict;
use warnings;

use parent qw( Encode::Encoding );

__PACKAGE__->Define( 'rot13' );

sub encode($$;$){
  my( $obj, $str, $chk ) = @_;
  $str =~ tr/A-Za-z/N-ZA-Mn-za-m/;
  $_[1] = '' if $chk; # $_[1] is aliased through the call. Inplace edit.
  return $str;
}

no warnings 'once';
*Encode::ROT13::decode = \&encode; # Because rot13( rot13() ) is a round-trip.

1;


package main;

use strict;
use warnings;


##</code><code>##

use Data::Dump ; 
dd\%Encode::Encoding;
for my $enc ( qw/
 :rot13
 :ROT13
 :encoding(rot13)
 :encoding(ROT13)
 :UTF-7
 :encoding(UTF-7)
 :via(ROT13)
 :via(Encode::ROT13)
                / )
{
    fudge( $enc );
}
dd\%Encode::Encoding;

our $tell;
sub fudge {
    my( $layer ) = @_;
    $tell ||= tell DATA;
    seek DATA, $tell, 0;
    print "## binmode DATA, $layer \n";
    binmode DATA, $layer;
    dd [<DATA>];
}
__DATA__
Apple
cat
dog
strawberry
watermelon


##</code><code>##

$ perl fudge
{
  "ascii"        => bless(do{\(my $o = 1783919988)}, "Encode::XS"),
  "ascii-ctrl"   => bless(do{\(my $o = 1783919960)}, "Encode::XS"),
  "iso-8859-1"   => bless(do{\(my $o = 1783919932)}, "Encode::XS"),
  "null"         => bless(do{\(my $o = 1783919904)}, "Encode::XS"),
  "rot13"        => bless({ Name => "rot13" }, "Encode::ROT13"),
  "Unicode"      => bless({ Name => "Internal" }, "Encode::Internal"),
  "utf-8-strict" => bless({ Name => "utf-8-strict", strict_utf8 => 1 }, "Encode::utf8"),
  "utf8"         => bless({ Name => "utf8" }, "Encode::utf8"),
}
## binmode DATA, :rot13
Unknown PerlIO layer "rot13" at fudge line 51.
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :ROT13
Unknown PerlIO layer "ROT13" at fudge line 51, <DATA> line 5.
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :encoding(rot13)
["Nccyr\n", "png\n", "qbt\n", "fgenjoreel\n", "jngrezryba\n"]
## binmode DATA, :encoding(ROT13)
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :UTF-7
Unknown PerlIO layer "UTF" at fudge line 51, <DATA> line 20.
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :encoding(UTF-7)
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :via(ROT13)
Cannot find package 'ROT13' at fudge line 51, <DATA> line 30.
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
## binmode DATA, :via(Encode::ROT13)
["Apple\n", "cat\n", "dog\n", "strawberry\n", "watermelon\n"]
{
  "ascii"        => bless(do{\(my $o = 1783919988)}, "Encode::XS"),
  "ascii-ctrl"   => bless(do{\(my $o = 1783919960)}, "Encode::XS"),
  "iso-8859-1"   => bless(do{\(my $o = 1783919932)}, "Encode::XS"),
  "null"         => bless(do{\(my $o = 1783919904)}, "Encode::XS"),
  "rot13"        => bless({ Name => "rot13" }, "Encode::ROT13"),
  "UCS-2BE"      => bless({ endian => "n", Name => "UCS-2BE", size => 2, ucs2 => 1 }, "Encode::Unicode"),
  "UCS-2LE"      => bless({ endian => "v", Name => "UCS-2LE", size => 2, ucs2 => 1 }, "Encode::Unicode"),
  "Unicode"      => bless({ Name => "Internal" }, "Encode::Internal"),
  "UTF-16"       => bless({ endian => "", Name => "UTF-16", size => 2, ucs2 => "" }, "Encode::Unicode"),
  "UTF-16BE"     => bless({ endian => "n", Name => "UTF-16BE", size => 2, ucs2 => "" }, "Encode::Unicode"),
  "UTF-16LE"     => bless({ endian => "v", Name => "UTF-16LE", size => 2, ucs2 => "" }, "Encode::Unicode"),
  "UTF-32"       => bless({ endian => "", Name => "UTF-32", size => 4, ucs2 => "" }, "Encode::Unicode"),
  "UTF-32BE"     => bless({ endian => "N", Name => "UTF-32BE", size => 4, ucs2 => "" }, "Encode::Unicode"),
  "UTF-32LE"     => bless({ endian => "V", Name => "UTF-32LE", size => 4, ucs2 => "" }, "Encode::Unicode"),
  "UTF-7"        => bless({ Name => "UTF-7" }, "Encode::Unicode::UTF7"),
  "utf-8-strict" => bless({ Name => "utf-8-strict", strict_utf8 => 1 }, "Encode::utf8"),
  "utf8"         => bless({ Name => "utf8" }, "Encode::utf8"),
}