Sometimes I see people use http://codepad.org as a way to quickly run/test their Perl snippets (it supports doing that with a wide variety of languages, from C to Scheme to Perl).

It's pretty obvious that there must be some limitations as to what code/features can be tested with codepad - does anyone know what those limitations are for Perl runner?

I'll get the ball rolling on my own observation: not every CPAN module is available :(