We'd like to make a conclusion of the recent discussion on firstname.lastname@example.org about a central wiki for Perl. First of all, perl.net.au by the Australian Perl Mongers, was voluntereed as a central MediaWiki instance for the Perl world. A different volunteer registered perl.wikia.com at Wikia (a community MediaWiki-hosting formerly known as WikiCities). At the moment, it mostly just refers to perl.net.au.
Finally, Ask Bjørn Hansen said he'd like to set up a Socialtext-based wiki once it is released as beta and he "would play with it" at possibly wiki.perl.org. However, meanwhile, one should probably start contributing to perl.net.au instead.
One should note that merlyn claims he suggested the idea of a central wiki for Perl (at Wikia) back in August 2005, so he also deserves some credit.