I'm probably too busy today to understand. We wanted to escape the strings so they can be used in a transliteration, right? Why not test it directly, then? 
sub use_it {
    my ($string, $search, $replace) = @_;
    my ($s, $r);
    $s = escape_metas('/', '\\') for $search;
    $r = escape_metas('/', '\\') for $replace;
    return eval "\$string =~ tr/$s/$r/r"
}

sub cheat {
    my ($string, $search, $replace) = @_;
    return eval "\$string =~ tr|\Q$search\E|\Q$replace\E|r"
}

sub simulate {
    my ($string, $search, $replace) = @_;
    my $result = $string;
    for my $i (0 .. length($search) - 1) {
        my $from = substr $search, $i, 1;
        my $to   = substr $replace, $i, 1;
        $result =~ s/\Q$from/$to/g;
    }
    return $result
}

for my $case (
    # String      search replace expect
    ['a/b'     => 'a/b',  'xyz', 'xyz'],
    ['a\\b'    => 'a\\b', 'xyz', 'xyz'],
    ['a/b'     => '\\/',  'xy',  'ayb'],
    ['a\\/b'   => '\\/',  'xy',  'axyb'],
    ['a/\\b'   => '\\/',  'xy',  'ayxb'],
    ['a\\\\b'  => '\\/',  'xy',  'axxb'],
    ['a\\\\/b' => '\\/',  'xy',  'axxyb'],
) {
    is simulate(@$case), $case->[-1], 'simulate';
    is cheat(@$case), simulate(@$case), 'cheat';
    is use_it(@$case), simulate(@$case), 'use';
}

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I'm not sure I got the "expect" right, but both "simulate" and "cheat" give the same results. "use", on the other hand, doesn't. I based it on your escape_metas - what did I do wrong?

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re^3: Transform ASCII into UniCode (escape_metas) by choroba
in thread Transform ASCII into UniCode by Perlian

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