Earlier quoted context omitted.
http://pl1.php.net/extract OMG, it's horrible :D
Why there isn't a flashing red warning label at the very top of that page, I have no idea. This is one instance where I would actually sanction using the tag.
None of which the 4chan code actually uses.
I've never seen the utility of extract -- it's the recommended way of getting wordpress plugin parameters, but to me, just using whatever array you're extracting from is always a better solution.