`chpp' is a preprocessor. Therefore, its main purpose is to modify
input text by including other input files and by macro expansion.

What distinguishes `chpp' from other textprocessors are mainly two
features:

* `chpp' is non-intrusive. This means that you can take your
     favourite text and it is very unlikely that it will be changed when
     piped through `chpp'. Due to this feature it is pretty easy to
     start using `chpp' since you can just start writing your text and
     need not concern yourself with `chpp' sitting in the background
     changing it for no obvious reason.

* `chpp' is not just a package for performing simple macro expansion,
     but can indeed be considered a full-fledged programming language.
     Most importantly, it provides support for complex data structures,
     namely lists and hashes (associative arrays), which can be nested
     arbitrarily.

WWW: http://www.complang.tuwien.ac.at/~schani/chpp/