See Using GPL'd Perl Modules in Commercial Software :)

Update: To answer a few of your questions within this thread (keeping in mind that I'm not a lawyer)...

Can my script be licenced under the GNU GPL licence even if its sold for a small fee?

Yes. The GPL Faq states: "You can charge nothing, a penny, a dollar, or a billion dollars. It's up to you, and the marketplace, so don't complain to us if nobody wants to pay a billion dollars for a copy.". The point of the GPL is to keep software free as in speech, not to prevent people from profiting from it.

Also, what about modules that's copyright are 'This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.'? Any difference?

Perl is dual licensed under the GPL and the Artistic license, if you abide by the GPL you won't run into any problems. If you want to avoid certain responsibilities required by the GPL, you could read up on the Artistic license (but you don't want to do that :).

If I soley just 'use' the module, no overiding of it or anything, is that acceptable?

This is the tricky part. As tilly noted in a response in Using GPL'd Perl Modules in Commercial Software 'One of the big grey areas in the GPL is the question of what a "derivative work" is.' This may or may not require you to license your script under the GPL if you're using GPL'd modules.

So you can charge for your work if it's released under the GPL, but keep in mind it also has to comply with the license, meaning other people could modify it, gives it to friends, or sell it as well. A good approach might be to release it under the GPL and charge for the installation and customization of it.