Markdent - Event Based Markdown Parsing
Markdown is a convenient format for wikis, comments, and any other sort of user input. However, parsing it is painful, and the existing Perl tools are limited to turning Markdown straight into HTML.
Markdent is an event-generating parser (think SAX). Using Markdent, you can explore Markdown documents in all sorts of interesting ways.
You could extract all of the links in a document, turn it into plain text, pull out headers to build a table of contents, and of course turn it into HTML.