A lot of good suggestions already. I'd like to add and reinforce a few.

• Maybe check out a YAPC if you haven't? A _LOT_ of fun.
• ORM's (DBIC,Rose,etc) are interesting and worth learning.
• Event Driven programming with POE is certainly a worthwhile excursion. All of my monitoring scripts and various daemons are POE based now.
• MVC Frameworks! (Catalyst/Jifty)
• If you're doing web stuff, why not pick up a JavaScript framework or two? I've heard and read good things about the following: ExtJS, jQuery, Dojo, and YUI.

Just a a few ideas. I'm actually still playing with that list. There's years of learning there.