source: vendor/perl/5.8.8/t/uni/chomp.t

#!./perl -w

BEGIN {
    if ($ENV{'PERL_CORE'}){
        chdir 't';
        @INC = '../lib';
    }
    require Config; import Config;
    if ($Config{'extensions'} !~ /\bEncode\b/) {
      print "1..0 # Skip: Encode was not built\n";
      exit 0;
    }
    if (ord("A") == 193) {
        print "1..0 # Skip: EBCDIC\n";
        exit 0;
    }
    unless (PerlIO::Layer->find('perlio')){
        print "1..0 # Skip: PerlIO required\n";
        exit 0;
    }
    if ($ENV{PERL_CORE_MINITEST}) {
        print "1..0 # Skip: no dynamic loading on miniperl, no Encode\n";
        exit 0;
    }
}

use Encode;
use strict;
use Test::More;

# %mbchars = (encoding => { bytes => utf8, ... }, ...);
# * pack('C*') is expected to return bytes even if ${^ENCODING} is true.
our %mbchars = (
    'big-5' => {
        pack('C*', 0x40)       => pack('U*', 0x40), # COMMERCIAL AT
        pack('C*', 0xA4, 0x40) => "\x{4E00}",       # CJK-4E00
    },
    'euc-jp' => {
        pack('C*', 0xB0, 0xA1)       => "\x{4E9C}", # CJK-4E9C
        pack('C*', 0x8F, 0xB0, 0xA1) => "\x{4E02}", # CJK-4E02
    },
    'shift-jis' => {
        pack('C*', 0xA9)       => "\x{FF69}", # halfwidth katakana small U
        pack('C*', 0x82, 0xA9) => "\x{304B}", # hiragana KA
    },
);

# 4 == @char; paired tests inside 3 nested loops,
# plus extra pair of tests in a loop, plus extra pair of tests.
plan tests => 2 * (4 ** 3 + 4 + 1) * (keys %mbchars);

for my $enc (sort keys %mbchars) {
    local ${^ENCODING} = find_encoding($enc);
    my @char = (sort(keys   %{ $mbchars{$enc} }),
                sort(values %{ $mbchars{$enc} }));

    for my $rs (@char) {
        local $/ = $rs;
        for my $start (@char) {
            for my $end (@char) {
                my $string = $start.$end;
                my ($expect, $return);
                if ($end eq $rs) {
                    $expect = $start;
                    # The answer will always be a length in utf8, even if the
                    # scalar was encoded with a different length
                    $return = length ($end . "\x{100}") - 1;
                } else {
                    $expect = $string;
                    $return = 0;
                }
                is (chomp ($string), $return);
                is ($string, $expect); # "$enc \$/=$rs $start $end"
            }
        }
        # chomp should not stringify references unless it decides to modify
        # them
        $_ = [];
        my $got = chomp();
        is ($got, 0);
        is (ref($_), "ARRAY", "chomp ref (no modify)");
    }

    $/ = ")";  # the last char of something like "ARRAY(0x80ff6e4)"
    my $got = chomp();
    is ($got, 1);
    ok (!ref($_), "chomp ref (modify)");
}