If you did not know already, Perl is another extremely popular open source interpreted programming language.
If you have ever tried writing a large program in Perl, you would have answered this question yourself! In other words, Perl is an excellent choice for small hacks and programs. However, Perl programs become unwieldy once you start writing bigger programs.
When compared to Perl, Python programs are definitely simpler, clearer, easier to write and hence more understandable and maintainable. Personally, I like Perl and use it on a daily basis but everytime I start to write a program, I think in terms of Python because it feels so natural. Also, Perl has undergone so many hacks and changes that it feels like one big (but one hell of a) hack. Sadly, the upcoming Perl 6 does not seem to be making any improvements regarding the readability of the language.
The only and very significant advantage that Perl has is its huge CPAN library - the Comprehensive Perl Archive Network. As the name suggests, this is a humongous collection of Perl modules (modules are reusable programs) and it is simply amazing because of its sheer size and depth - you can do virtually anything you can do with a computer using the CPAN modules. One of the reasons that Perl has more libraries than Python is that it has been around for a much longer time than Python.
Another thing to note is that the in-progress Parrot virtual machine is designed to run both the completely redesigned Perl 6 as well as Python and other interpreted languages like Ruby and PHP. What this means is that maybe in future, we will be able to use all the Perl modules from Python which combines the best of both worlds. However, we will have to wait and see when Parrot becomes ready for that.