func caesar(msg, key, decode=false) {
    decode && (key = (26 - key));
    msg.gsub(/([A-Z])/i, {|c| ((c.uc.ord - 65 + key) % 26) + 65 -> chr});
};

var msg = 'THE FIVE BOXING WIZARDS JUMP QUICKLY';

var enc = caesar(msg, 10);
var dec = caesar(enc, 10, true);

say "msg: #{msg}";
say "enc: #{enc}";
say "dec: #{dec}";