A question to ask yourself is: is it better to know a few languages really well or to know the basics only of many languages?
in reply to Next Language to Learn
It is my experience that unless you regularly use a language you tend to loose your edge in it. I used Visual Basic and Visual Basic for Applications for many years and although the basics are still there, every two lines of code I write I have to consult the manual now and I do not have the subtle shortcuts and nice features "on call" anymore.
Another path to follow is perhaps to add languages such as SQL or (La)Tex to your toolkit, these are things which can leverage your use of Perl to a higher level.
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James