Anonymous Monk,
I have read through their Terms Of Service and verified there is no mention of prohibition of (bot, crawler, automated login, etc). You are on the right track with WWW::Mechanize. You may run into problems if the site uses Javascript or cookies. Typically what I do is use the Firebug plug-in to Firefox. Then, I examine the interaction with the website and duplicate it.

If you can convince me this is for a legitimate purpose, I would be willing to write a fully working program that logs in.