Perl-based Wiki clone

 UseMod is a reimplementation/clone of the original Wiki concept
 created by Ward Cunningham. A "wiki" is a website that is
 collaboratively edited by its users, including the ability to alter
 text written by other users.
 .
 UseMod provides common wiki features as well as unique features:
 recent changes, conflict resolution, difference links, subpages,
 interwiki links, full text searching, free links (for free-form wiki
 names), administrative features.