Angerwhale is Perl-based bloging software that reads posts from the filesystem, and determines authorship based on the post's PGP digital signature. These posts can be in a variety of formats (text, wiki, HTML, POD), and new formats can be added dynamically at runtime. Posting comments is also supported, and again, authorship is determined by checking the digital signature.
Features include guaranteed valid XHTML 1.1 output, social tagging, categories, syntax highlighting (see http://blog.jrock.us/articles/Syntax%20Highlighting.pod for details), RSS and YAML feeds for every article, comment, tag, and category, nested comments, intelligent caching of everything, space-conserving mini-posts, search-engine (and human!) friendly archiving, a flashy default theme, and lots of other cool stuff.
At one point, Open Hub analyzed source code for this project based on code location(s) available at that time. Since then, the code locations have been removed.