I have been having this urge of using a wiki written in Perl for PerlChina. We used instiki(in ruby) before moving to mediawiki(in PHP). Reason why we use mediawiki is because Instiki was not stable at the time, Yahoo China happens to run few mediawiki for other OSS sites so it is easy for them to adopt us.
We need a wiki for collaborating on local meetup, communication between members for projects and hosting Chinese documentations, well there is a lot we can put in use with a wiki. Since we are a Perl user group and eating own dog food makes a lot of sense.
A good wiki in my book should be easy to install and maintain. has spam protection and ACL control. good web interface for managing wiki. should be file based and easy to customize through template. Personally I rate dokuwiki highly. pmwiki is not bad either.
Perl Wiki that comes closed to what I want are foswiki (twiki fork) and ikiwiki. foswiki has lots features but It doesn't have a good reputation for code quality. Ikiwiki is ok but it took me much more time to have it up and running than either dokuwiki or pmwiki. And it has much smaller community than the other two and fewer features. If I had to pick a perl wiki, I would have to go with ikiwiki.
Keep in mind, We don't get root access on the system and the way PHP wiki drop in and just work just makes me envy. Why can't we have something like that? oh.. I digress.
enough rant. I go back to mediawiki.
UPDATE: I should mention that oddmuse is also a good choice. It is very easy to install, stable with lots plug-ins.