UBB has been discussed previously, both
here and on usenet (do a google search), and the verdict seems to be that it pretty much sucks. Sloppy coding practices, etc. I would stay away from it.
Unfortunatly, I don't have any better suggestions. I installed PostNuke on my work machine yesterday and it seems pretty capable (and easy to install provided that you've got MySql and PHP running). But it's not a perl solution, no.
Writing your own forums software is certainly doable, but far from trivial.
Cheers,
-- moodster