After programming Perl for a year or two. :) I have a couple of things I could add.

Effective Perl Programming is excellent. I would grab it every once and a while and read a section. Do that enough times and its bound to sink in.

The same goes for The Perl Cookbook.

Depending on what you do, have a look at Mastering Regular Expressions.

Do you have a Perl Monger's group in your area?