If you're worried about subclassing considerations, how about something like Net::IRCTool::BotName? This creates a new level called 'IRCTool' for IRC Tools to use, and BotName is whatever you name your module (maybe Net::IRCTool::BUU). It also leaves the door open for other people to release other IRC Tool modules, without causing confusion that something like Net::IRC::Tool or Net::IRC::BUU would cause.