What the previous post mentions will get all the files, if you dont do the grep command. (the last command, separated from the others). You should probably do some reading. For this one, read about opendir().

There is plenty of great documentation about built-in commands at perlmonks, but you should also get some books. I'd start with Programming Perl, published by O'Reilly & Assoc, if you have reasonable programming experience in other languages. - Its a great reference, particularly Chapter 29: Perl Funcitons in Alphabetical Order

If you're new to programming in general, you may want to get O'reillys Learning Perl