require('Math::Random::ISAAC')

func xor_isaac(key, msg) {
  var rng = %O<Math::Random::ISAAC>.new(unpack('C*', key))

  msg.chars»ord()»                                          \
    -> »^« 256.of{ rng.irand % 95 + 32 }.last(msg.len).flip \
    -> «%« '%02X' -> join
}

var msg = 'a Top Secret secret'
var key = 'this is my secret key'

var enc = xor_isaac(key, msg)
var dec = xor_isaac(key, pack('H*', enc))

say "Message: #{msg}"
say "Key    : #{key}"
say "XOR    : #{enc}"
say "XOR dcr: #{pack('H*', dec)}"