Bet the farm. Python or PHP?
mechanical_fish: calendar/scheduling/notifications with some social networking and people matching/search functionality. The site will be highly configurable/maintainable by its community from establishing/interacting within groups to tweeking page layouts.How much of your app can be built by hooking together existing Drupal modules?If the answer is "lots" -- and because your brief description sounds like a long list of stock parts from the Social Network aisle at Costco, I wouldn't be surprised if it is -- perhaps you should consider Drupal. Which means PHP, alas, but that's a small price to pay for avoiding the annoyance of building every single one of your site's 120,000 proposed features yourself, from scratch.If the answer is "a lot, except for features X and Y, and I hate Drupal's existing, buggy options for Z" the Drupal community will be really happy to see you develop and contribute open-source code that can do X and Y. And we probably all hate Z, so fix it and you'll be our hero. You'll have plenty of time to work on Z because you won't be spending time redeveloping things like "basic user logins with emailed password reminders", or "users can create and join groups which have their own subsites" from scratch -- yet again -- in a language whose idioms you haven't learned yet.If the answer is "not much"... may I suggest that you seriously reduce the scope of your first project?Of course, if the proposed app is less of an actual future product than it is an excuse to broaden your mind by learning a language that's not Perl or Java, you should probably grab onto Python or Ruby with both hands. PHP has many practical features, but it doesn't have much to teach a Perl programmer.