7.4. POD Extensions
POD has some extended dialects with more features and options:
PseudoPod is an extended set of Pod tags used for book manuscripts. Standard Pod doesn't have all the markup options you need to mark up files for publishing production. PseudoPod adds a few extra tags for footnotes, tables, sidebars, etc.
MJD's POD variant called MOD - this was used to write the book "Higher Order Perl", and one can download the markup for the book and for source code for the MOD package from the book's site
Perldoc.pm was an attempt to modernise POD by Ingy döt Net, and incorporating some markup from his Kwiki wiki engine.
Aside from that, Wikipedia has a list of other Lightweight markup languages, and some of them also have implementations in Perl.