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my $message = "hello world";
my $key = "test";
use v5.38;
my $enc = vigenere(0, $key, $message);
say "Encoded message: $enc";
my $dec = vigenere(1, $key, $enc);
say "Decoded message: $dec";
# mode = 0 to encode, 1 to decode
sub vigenere($mode, $key, $message) {
my $alph = "abcdefghijklmnopqrstuvwxyz";
my $q = (length $message) / (length $key);
$key .= $key x $q;
while (length $key > length $message) {
$key = substr $key, 0, -1;
}
my @msg_letters = split "", lc $message;
my @key_letters = split "", lc $key;
my @rots = map {index $alph, $_} @key_letters;
my @ans_letters;
for my $i (0 .. $#msg_letters) {
if ($msg_letters[$i] =~ /\W/) {
push @ans_letters, $msg_letters[$i];
next;
}
my $v = index $alph, $msg_letters[$i];
my $x = ($mode == 0) ? ($v + $rots[$i]) % 26 : ($v - $rots[$i]) % 26;
my $let = substr $alph, $x, 1;
push @ans_letters, $let;
}
return join "", @ans_letters;
}
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