I'd have to agree with moritz, I know of no module that will do this for you but KinoSearch may be a great place to start (I've done similar apps with KinoSearch's soulmate Lucene). Also, I've been reading Collective Intelligence which goes into detail about the algorithms to do this type of app. All of the examples are in Python but I have yet to come across any of the examples that I could not translate easily into perl (and I know nothing about Python).