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.
TXR - Pragmatic, convenient data munging language.
XMLStarlet - XMLStarlet Command Line XML Toolkit
AWK - Linux users can perform many types of searching, replacing and report generating tasks by using awk, grep and sed commands.
xmllint - command line XML tool