..beacause it's really worth the effort to learn it.
Really you can start doing simple things in a simple way and then discover that there is always a perlish way to front a new problem: complex data structures, DBI, CGI, Tk, sockets, image manipulation, math, LWP, web frameworks, PSGI and Plack, XML, regular expressions, Moose...
Because Perl let you to be free (as in freedom): from a glue script to an introspected translucent OO system you can choose your way to do the work.
Beacause there are good book to read about it on every step of your learning curve: my first love (wonderfull for a newcomer to Perl, even if somehow outdated)Perl Cookbook, High Order Perl, Modern Perl...
Because of oneliners: when you master some switch the console becomes a playground...
Beacause you can easily write portable programs. More: if you run on win you can produce standalone exucutables and use portable Perl gently Strawberry flawored...
Because of cpan and perlmonks..
Because the magic is at your disposal: BEGIN and company,__DATA__,signals, symbol table. The compiler is by your side, invisible but present: eval!
Because if you learn it well you'll be rewarded in the escathological day of Perl 6 advent... ;=)
there are no rules, there are no thumbs..