Perl - Highly capable, feature-rich programming language with over 26 years of development
GNU M4 - GNU M4 is an implementation of the m4 macro preprocessor.
AWK - Linux users can perform many types of searching, replacing and report generating tasks by using awk, grep and sed commands.
XMLStarlet - XMLStarlet Command Line XML Toolkit
Ruby - A dynamic, interpreted, open source programming language with a focus on simplicity and productivity
xmllint - command line XML tool