The answer is quire obvious:
Perl is hegemonic
- it has a single point of access to ALL its libraries - CPAN
- its description is more than compelling saying that The Comprehensive Perl Archive Network (CPAN) currently has 100,462 Perl modules in 23,551 distributions, written by 9,266 authors, mirrored on 269 servers. The archive has been online since October 1995 and is constantly growing.
- finding modules requires just a search on http://search.cpan.org/
- installing perl modules is a really simple task, most of the time issuing a
at the command line being sufficient
- the community is simply awesome, the fastest and most efficient way to get help is to go on irc on the perl irc channels and ask there.
- I have also seen some of the world perl gurus activating on stackoverflow
- beside all of these, perl has cpan testers which provides multi-platform testing for modules. Today there are over 15 million tester reports and more than 100 testers each month giving valuable feedback for users and authors alike.
Regarding other programming languages, I think that Ruby is the one closest to copying the CPAN model