|XP is just a number|
I find that setting a goal to which I'm committed is key to learning a new piece of technology. Perl is a language and, just like a spoken language, you need to get comfortable using it, then actually use it regularly, to maintain the skill.
I've tried to teach myself several languages in the past, but Perl is the only one that took at all because I used it to solve problems. More importantly, I used it to solve problems I was really invested in solving.
So, I recommend that you find a problem to solve! Find something at home or at work that you can automate in some way, some problem that a nice bit of Perl can solve for you, then work at making that problem go away. Then, do it again. Rinse, repeat, as necessary.
Remember, this doesn't have to be an "official" problem or project, just something that you can use Perl to solve, or automate, or improve. It may mean spending some of your own, personal time to work on it, but, if that ends up helping you at the job, and gets you into a position where you can use Perl for work in an official, sanctioned way, then it'll be worth it, right?
Also? Start small and work up. Pick a small project that can maybe grow into more projects or a larger project.
The most important thing is to just go for it! Then come back and share your results, both good and bad, and work on your skills. You'll be surprised how quickly you get better at it. Honest.