I code in Python at work, but all of my open source software is written in Perl (well, C, C#, Javascript/JQuery too, but I digress).

Python is a very good entry level language, but it is also extremely powerful and easy-to-use language for very large projects with many developers.

Although I favour Perl even if it didn't have them, the two most important features of Perl that I can't get anywhere else is the CPAN, and the extreme ease in which unit tests can be written and run, as well as how simple it is to find out exactly what's wrong and where. Unit testing is not so simple in Python, and given that my unit test suite contains usually > 10 times the amount of code my projects do, I need it to be easy.