No, you don't need to be a part of Grand Creation to write quests. Though, I do recommend checking us out to see everything in action. All the work we do is publically available via CVS and from time to time, will be officially released. So, we aren't a closed sub-community at all.
Your Perl skill level is no concern, there are tons of quests available. You can start small and learn then move on to harder stuff. The quest team isn't structured at all. Nobody is going to tell you what you have to do and there are no deadlines
I appreciate and welcome any work done by anybody.