is used by many scripts - most are unmaintained. Many invoke /usr/bin/env python, a couple invoke /usr/bin/python. It is not generally known if these will work with a symlink to python3 (as used in some distros) and two from pythontex invoke python2. is used by some scripts, mostly within mtx_context which is part of conTeXt, but also for one or two others, such as match_parens, which are generally useful. The perl module Tk, which needs to be run from an X11 session to run the tests and requires , is used by one of the scripts for ptex (Japanese vertical writing), can be used by a conTeXt texfind script, and is needed for texdoctk (a GUI interface for finding documentation files and opening them with the appropriate viewer).