My opinion as I am not a lawyer:

Probably the safest way is to not use any modules that are ONLY licensed with GPL...Most modules seem to be under the Perl Artistic AND GPL, so you would "choose" the Artistic one ;-) (Some popular Win32:: ones are exceptions and are only released under GPL)

I *think* I did read a comment from Larry about this...(perl.com maybe?), and he seemed to favor the view that you could "use" a GPL'd module and not have to release your product under the GPL license...but he wouldn't be the one deciding to sue you, it would be the GPL folks...

Bottom line seems to be if you use GPL, you need to follow the GPL