HTML PLAIN is a "HTML Preprocessor Lacking An Interesting Name". Symbolic names instead of filenames allows files to be moved around without breaking links. Templates allow easy customization and changes of the layout. Tags can be redefined for a better structure of the document. Beginners can use one of the given templates and do not have to use any markup language at all. Experts can write their own Perl macros in order to get access to metadata and more flexibility.
