XSLT syntax highlighting is an implementation of syntax highlighting as an extension module for Java based XSLT processors (such as Xalan or Saxon). For example, if you have an article about programming written in DocBook, code examples can be automatically syntax highlighted during the XSLT processing phase.
rgxg (ReGular eXpression Generator) is a C library and a command-line tool that generate (extended) regular expressions. It can be useful for generating expressions that match, for example, a specific number range (e.g. 0 to 31 or 00 to FF) or all addresses in a CIDR block (e.g. 192.168.0.0/24 or 2001:db8:aaaa::/64).