I was under the vauge impression (quite possibly from slashdot), that if you used any code that was under gpl, you had to release the *entire* code.

First of all, don't believe everything you read on Slashdot ;-).

I did bring this up in relation to modules in a previous thread. As maverick pointed out, it may depend on how you define 'use'. It's very questionable and I'm still not clear whether or not this would be a violation of the GPL.

As for simply taking code licensed under the GPL, cutting and pasting it into your own code, and not releasing it, that definately is a violation.

Update: Aha! I found something. From the GPL Faq 'If interpreter is released under the GPL...' section:

A consequence is that if you choose to use GPL'd Perl modules or Java classes in your program, you must release the program in a GPL-compatible way, regardless of the license used in the Perl or Java interpreter that the combined Perl or Java program will run on.

That appears to be pretty clear. If you use modules that are only licensed under the GPL, you need to release your program under a GPL-compatible license.