GNU M4 - GNU M4 is an implementation of the m4 macro preprocessor.
Gema - General purpose text macro processor.
GCC C Preprocessor (cpp) - Top (The C Preprocessor)
PP - A generic Preprocessor - P is a text preprocessor designed for Pandoc (and more generally Markdown and reStructuredText).
XMLStarlet - XMLStarlet Command Line XML Toolkit
Filepp - filepp is a generic file preprocessor.