GPP - GPP is a general-purpose preprocessor with customizable syntax, suitable for a wide range of...
xmllint - command line XML tool
GNU M4 - GNU M4 is an implementation of the m4 macro preprocessor.
Python - Python is a clear and powerful object-oriented programming language, comparable to Perl, Ruby, Scheme, or Java.
GCC C Preprocessor (cpp) - Top (The C Preprocessor)
XMLStarlet - XMLStarlet Command Line XML Toolkit