I work in both perl and PHP. I am working now at porting a PHP system back to perl (where a much earlier version was originally developed).
What I have found, in my personal consulting work with organizations needing both perl and PHP folks, is that the perl folks can work in both environments fairly well, but the PHP folks don't seem as able to.
My conclusion is that the skills / capabilities / capacities / whatever needed to be a skilled perl programmer are high enough that an above average perl programmer can easily be a significantly-above-average PHP programmer.
Take session management. My PHP framework took session management for granted. It was just there and worked. For a perl programmer who had to develop a session management module, that felt like heaven. Ditto with things like sending emails.
For a perl programmer to be able to handle those (relatively complex) issues, you either spend time programming it, or searching CPAN to find an already built solution.
Some might see that as a "weakness" of perl, but the strengh that comes from this is just what is pointed out here: just a "normal" perl user here is a top-five-percent PHP programmer.
I see perl programmers capable of looking at problems and finding multiple solutions -- and virtually everything we might see as a possibility is also part of the PHP language. So most perl programmers, IMNSHO, would be better than average PHP programmers. Yet most PHP programmers I have worked with seem to struggle to learn perl.
I'm a perl programmer by choice -- which is why I am porting my PHP work back to perl. It is powerful enough to handle every task I have thrown at it. What else can you ask of a programming language?
So my advice? Stick with perl; keep PHP in your back pocket. If someone needs those services, then coolness. Otherwise, keep up the good work!!!