Of all things that which is the most important skill for any programmer to develop is that of humility.
As far as Perl goes...
Firstly, write for maintenance, use strict/warnings all the time and just because you can do it in 1 line doesn't always mean you should. There are 2 people you care about when writing any program, yourself at 4am and yourself 6 months from now. Perl as lovely as she is can be a cruel mistress when you're half-awake... If you write well tested code that meets requirements you will make those 2 people happy and as a by-product everybody else that will eventually touch your code as well.
Learn regular expressions and EVERYTHING about them, from back-references to the meta-characters and symbols and all their little nuances as what is most efficient, as to when they will be compiled, or when they will be recompiled. Also learn what your best practices are as far as readability of those regular expressions and most importantly write test-cases for your regular expressions. Tests that succeed, tests that fail, and tests that do nothing (aggravatingly enough that happens plenty).
Lastly, and this has nothing to do with perl, just a general tip for anybody that is younger and starting out in a programming profession. Make sure that your office setup is as ergonomic as possible, carpal/cubital tunnel is a bane for those of us who have been doing professional computer work for many years. Find yourself a great ergonomic keyboard, ergonomic mouse, keyboard tray, chair, etc..., and don't forget to take a break every now and then. I've had carpal tunnel surgery on both wrists and will probably need cubital tunnel surgery on my left elbow and I'm still in my 30's. Take it for what you will, we all get older, time takes it toll no matter how good you feel now. :)