PodWiki by T.Linden uses Perl POD as its markup, which is an established language for documentation in the Perl community and well known world wide. PodWiki enhances POD a little to circumvent some lacking features (such as images or includes).
Beside POD, it also understands a shorthand markup which writes like natural text and is very easy to understand for new users. If they need more features they have to use POD; for simple pages WikiShorthand is enough.
PodWiki supports includes, graphics, version control (via RCS), diffs, merge-back, user/group authentication and authorization, page property inheritance, variables, attributes and a lot more. The user can use so called "formatters" to insert plain HTML or text content, which is very useful for a stylesheet or example C code. There is also a formatter for Perl code available which makes it possible to create interactive PodWiki pages (note: for security reasons this feature is turned off by default).
The big difference from other Perl WikiEngines is that PodWiki is 100% customizable, since the whole wiki site is driven by the include feature. PodWiki always loads one page ("AutoLoad"), which includes the other stuff, such as the Header, Stylesheet, Menu, the Content-Area, Edit-Bar, Footer and so forth. This allows the user to fully modify PodWiki's look-and-feel. It is therefore possible to create sites that doesn't look like a wiki at all, for example this one: http://www.haus-burg-fehmarn.de/.
If you are using Apache with mod_perl you can speed up PodWiki. It's mod_perl compliant.
Beside all those features it is still very easy to install, no need for lots of additional Perl modules or cryptic installation procedures. Just do:
./configure && make install
The configure script understands some parameters which allows tweaking the installation such as destination path or the like.
Download and documentation: http://www.daemon.de/PodWiki