In addition to BBEdit (which available in a pay version and a time-limited 'demo' version), Mac OS X also comes with Emacs and vi.

Both Emacs and vi run in Terminal. They are completely text based and don't have a graphical interface (well, they can, but we're not gonna talk about installing X and Fink). There are GUI based editors that are free (like JEdit).

You can read an Emacs tutorial here.

Vi tutorial available here.

You'll need to enter the examples in a text editor and then save it (perhaps as 'hello.pl'.

After saving the example, you run it by typing 'perl hello.pl'.

Welcome to Perl! Perlmonks is here to help, but please read documentation before asking a question. If you don't like reading docs in a Terminal, try perldoc.com.