coming from a shell scripting background where i used bash, awk, egrep and all those nice tools, i can give you the advice that you don't need another scripting language besides Perl.
the intention behind Perl was to build a scripting language that could do what bash, awk, sed and all the other tools could do, which wore around about 20 years ago. so learning php, phyton or ruby is not a bad idea, but i don't think it will give you mutch benefit over Perl. maybe it would be a good idea to learn something different, which can do things you can't with Perl. let's say JavaScript for browser scripting or C for compiled stand alone programs which are way faster that Perl scripts. also you could benefit from C by using Inline::C in your Perl scripts.