Purpose: explain the proper use of source and other means of including user function code into a running interpreter (wishrc/tclshrc/whatever). Also provide a launching point for discussions on send, use of socket based communications like the comm extension, and other alternatives.
See also How to change a running system - RS - This page demonstrates how long titles in the Wiki can be. Still, shorter titles might draw more links from other pages - it's just lazyness...
See also Writing Tk programs so that the user can do simple custimizations without modifying the application - too bad one can't easily consolidate these.