I assume you mean Crypt::IDEA:

Perldoc Crypt::IDEA

....
my $key = pack("H32", "0123456789ABCDEF0123456789ABCDEF");
my $cipher = new IDEA $key;
my $ciphertext = $cipher->encrypt("plaintex");  # NB - 8 bytes
print unpack("H16", $ciphertext), "\n";

However, this can not be used to encrypt the data between your webserver and the browser. If you want to do that you'll need to be running an SSL webserver.