I downloaded the source and looked through it, and I can't find any reference to a thought subroutine in the source code.

If you are really interested in writing an AIMBot, you really should review the documentation and samples that are included in the Net::AIM module. Aryeh Goldsmith included a sample program with the module called aimtest that is actually a really good reference to study while trying to learn how to use the module. The module itself is simple enough to use. You just add references to subroutines to handle the messages that are recieved from the AIM server.