A contrast that is often made is more to do with attitude and approach than language differences: Perl embraces diverse approaches to solving problems with no single favored technique (TIMTOWTDI) where Python embraces "The one true way".

Perl is very rich with a lot of stuff built into the language where Python depends more on external libraries to provide the same functionality. There is a system Perl on pretty much every version of *nix (OS X is a version of *nix under the hood) whereas Python generally has to be installed. Neither language is installed by default on Windows.

Python is used a lot in physical sciences contexts and for controlling hardware. Perl is used a lot in Biological sciences contexts and for file processing. Perl used also to be the language that ran the web and still does to a modest extent.