Interesting entry about Perl in Emacs (search for "using perl" in the page). It seems you can define Emacs functions in Perl, which would bring... *drumroll* CPAN to Emacs.
Haven't tried it yet, but it definitely sounds cool.
Bonus tip from the same page: you can define a marco when in dired mode, to apply changes to many files. Hmm... is there no other way to search and replace in many files?