This doesn't seem particularly like a Perl question... Could you show us some code you've already written? If so, then the Monks might be able to offer some suggestions, but your question is broad enough that you probably won't get much help.

You're looking for an algorithm to automatically classify texts based on their titles? Text classification (given an entire text) is a research area unto itself. My advisor got her Ph.D. doing text classification work. I'm sure that Google has lots of highly-paid professionals (or pigeons) doing their classification for them. Or software written by a talented team, anyway. :-)