[expeditious]

One thing is that Perl 5 doesn't include by default a number of modern features that Python and Ruby have OOTB. Easy OOP, exceptions, and named function args, to name a few. If you want these things for Perl, you need to dash out to the corner store (the CPAN) for them.

Also, Perl 5 tends to be used for a lot of unglamorous admin work. So, although almost everyone's got a few utilities or cron tasks on their system written in Perl, they're not shouting about it from the rooftops.

Also, Python is an easy language to learn, and so people like to learn it and blog about how easy/nice/shiny it is: http://xkcd.com/353/ .

[telemachos]

Ruby doesn't provide named function arguments. In my experience, Rubyists tend to do what Perlers do: use hashes to create quasi-named arguments to functions.