bot.rb

require 'socket'

s = TCPSocket.new 'irc.freenode.net', 6667
s.puts "NICK foo"
s.puts "USER foo 0 * :foo"
s.puts "JOIN #ruby"

loop do
  case msg = s.gets
  when /PING (\S+)/
    s.puts "PONG #$1"
  when /:>> (.+)/
    s.puts "PRIVMSG #ruby :#{eval $1}"
  end
end