gpp is a general-purpose preprocessor with customizable syntax, suitable for a
wide range of preprocessing tasks. Its independence on any programming
language makes it much more versatile than cpp, while its syntax is lighter
and more flexible than that of m4.

gpp is targeted at all common preprocessing tasks where cpp is not suitable
and where no very sophisticated features are needed. In order to be able to
process equally efficiently text files or source code in a variety of
languages, the syntax used by gpp is fully customizable. The handling of
comments and strings is especially advanced.

WWW: http://www.math.polytechnique.fr/cmat/auroux/prog/gpp.html