* I've had more years of Perl than I have of Ruby. While there's not a massive difference it comes a bit easier to my fingers and brain.
* The testing framework is better - it's much easier to integrate different styles of testing and integrate tests running in other languages
* I can usually get more people to do my work for me with CPAN than I can with rubygems
* Moose has some interestingly different ways of breaking up abstractions (Moose is the de facto way of doing OO in Perl now. Moose is to Perl as CLOS is to Lisp)
You're probably not going to be suddenly more productive if you switched to Perl - but there are some plus points. As does Ruby of course.
Swings or roundabouts. Your choice :-)