What everyone else is saying. Getting involved in a dev group can be a big growth catalyst too. Peer pressure and publicly viewed code (the code we write for others tends to be a lot better than that we write for our own projects; for me anyway) is a great way to learn. Moose community? Catalyst? Rose? DBIC?

Another excellent tactic for learning is to switch gears entirely. Try Ruby, Java, electronics projects... I found that working with Ajax and JavaScript changed my understanding of CGI/HTTP pretty dramatically even though I'd been doing CGI for years. Rooted out all the weak spots in my competencies. Slinging X(HT)?ML only became natural to me after learning to sling the DOM from JS.

After picking up any new technology you will find your Perl view improves. There are many interesting problem spaces being actively worked on. Social network stuff, distributed data, de-centralized security...

Another big winner is to pick up an abandoned CPAN module. Or start a new one for something like a new web service no one has had time to do yet. Forces you to learn deeper topics like testing and distribution.

Diving into the books can be nice -- I own just about all of them; some in multiple editions at this point -- but I find that I only absorb the stuff well when I can apply it to a problem space.