Xidel - Xidel is a command line tool to download html/xml pages and extract data from them using CSS 3 selectors, XPath 3 expressions or pattern-matching templates.
GNU M4 - GNU M4 is an implementation of the m4 macro preprocessor.
xmllint - command line XML tool
Gema - General purpose text macro processor.
XMLStarlet - XMLStarlet Command Line XML Toolkit
GCC C Preprocessor (cpp) - Top (The C Preprocessor)