You might want to consider something like:

    my @abc = ('a'..'z');
    my %abc = map { ($abc[$_],$_) } (0..25);
    my @key = map { $abc{ lc() } } $key =~ /([a-z])/ig;
[download]

To use it, loop through the characters in your message any way you like. The following assumes you have the current letter in $c , that $i holds your position in @key , and that the result will be in $result . . .

        my $new_c;
        if ($c =~ /[a-z]/i) {
            $new_c =  $abc[($abc{lc($c)} + $key[$i]) % 26];
            $new_c = uc($new_c) if ($c =~ /[A-Z]/);
            $result .= $new_c;
            $i = ($i + 1) % @key;
        } else {
            $result .= $c;
        }
[download]

You could use the same code above for decoding if you changed @key to hold negative numbers instead of positives.

-sauoq

"My two cents aren't worth a dime.";