HTML::TextToHTML converts plain text files to HTML. The txt2html
script uses this module to do the same from the command-line.

It supports headings, tables, lists, simple character markup, and
hyperlinking, and is highly customizable. It recognizes some of the
apparent structure of the source document (mostly whitespace and
typographic layout), and attempts to mark that structure explicitly
using HTML. The purpose for this tool is to provide an easier way of
converting existing text documents to HTML format, giving something
nicer than just whapping the text into a big PRE block.