source: vendor/perl/5.8.8/t/run/switchC.t

#!./perl -w

# Tests for the command-line switches

BEGIN {
    chdir 't' if -d 't';
    @INC = '../lib';
    unless (find PerlIO::Layer 'perlio') {
        print "1..0 # Skip: not perlio\n";
        exit 0;
    }
}

require "./test.pl";

plan(tests => 6);

my $r;

my @tmpfiles = ();
END { unlink @tmpfiles }

my $b = pack("C*", unpack("U0C*", pack("U",256)));

$r = runperl( switches => [ '-CO', '-w' ],
              prog     => 'print chr(256)',
              stderr   => 1 );
like( $r, qr/^$b(?:\r?\n)?$/s, '-CO: no warning on UTF-8 output' );

SKIP: {
    if (exists $ENV{PERL_UNICODE} &&
        ($ENV{PERL_UNICODE} eq "" || $ENV{PERL_UNICODE} =~ /[SO]/)) {
        skip(qq[cannot test with PERL_UNICODE locale "" or /[SO]/], 1);
    }
    $r = runperl( switches => [ '-CI', '-w' ],
                  prog     => 'print ord(<STDIN>)',
                  stderr   => 1,
                  stdin    => $b );
    like( $r, qr/^256(?:\r?\n)?$/s, '-CI: read in UTF-8 input' );
}

$r = runperl( switches => [ '-CE', '-w' ],
              prog     => 'warn chr(256), qq(\n)',
              stderr   => 1 );
like( $r, qr/^$b(?:\r?\n)?$/s, '-CE: UTF-8 stderr' );

$r = runperl( switches => [ '-Co', '-w' ],
              prog     => 'open(F, q(>out)); print F chr(256); close F',
              stderr   => 1 );
like( $r, qr/^$/s, '-Co: auto-UTF-8 open for output' );

push @tmpfiles, "out";

$r = runperl( switches => [ '-Ci', '-w' ],
              prog     => 'open(F, q(<out)); print ord(<F>); close F',
              stderr   => 1 );
like( $r, qr/^256(?:\r?\n)?$/s, '-Ci: auto-UTF-8 open for input' );

$r = runperl( switches => [ '-CA', '-w' ],
              prog     => 'print ord shift',
              stderr   => 1,
              args     => [ chr(256) ] );
like( $r, qr/^256(?:\r?\n)?$/s, '-CA: @ARGV' );