This is rit, it is a simple templating engine. It takes a text file, and a template file, and produces an output file. It can be extended with modules to do more if you feel so inclined.
I use this script to generate all html files on my web site. So it works pretty well. I have been using it for over a year now too. I wrote this because nothing else quite did what I needed, and I was bored.
Super simple example file included in the archive.