This page is about the Tcllib package. For a general discussion of the concept see GUID and UUID.
The uuid package provides a generator of universally unique identifiers (UUID) also known as globally unique identifiers (GUID).
Documentation can be found at https://core.tcl.tk/tcllib/doc/trunk/embedded/www/tcllib/files/modules/uuid/uuid.html
PYK 2016-01-29: Warning: This implementation uses info hostname, or exec ipconfig on Windows. I was once offline and a program of mine was hanging. This package turned out to be the culprit.