RuntimeObject["repl"] = proc do |receiver, caller|
    puts "Launching REPL : type \"die\" to exit."
    loop do
      line = Readline::readline(">> ")
      Readline::HISTORY.push(line)
      break if line == "die"
      message = Message.parse(line)
      value = message.call(Lobby) if line
      puts " => #{message.inspect}"
    end
  end