koala_bot is an IRC bot that sits in a channel watching for lines matching the regular expression /k.*o.*a.*l.*a/ and responds with a random line from a cool essay about koalas.
ruby koala_bot.rb server[:port] #channel [#channel2 ...]
You probably need to do this to use the gems included in the vendor/ directory:
ruby -rubygems -I vendor/ koala_bot.rb server[:port] #channel
ruby koala_bot.rb chat.freenode.net #koalas
Uses Net::YAIL and dependencies, but these come bundled with the bot in the vendor/ directory.