general-purpose preprocessor with customizable syntax

 GPP is a general-purpose preprocessor with customizable syntax, suitable for
 a wide range of preprocessing tasks. Its independence from any one
 programming language makes it much more versatile than the C preprocessor
 (cpp), while its syntax is lighter and more flexible than that of GNU m4.
 There are built-in macros for use with C/C++, LaTeX, HTML, XHTML, and Prolog
 files.