nsloopctl

Compatibility: The module compiles with Tcl 8.5, 8.6 and 9.0.

This module redefines Tcl's "for", "foreach", and "while" commands to allow
both the gathering of statistics about each loop, and also to provide a
mechanism to pause, cancel, and resume a particular loop. 

If an interp is stuck in something other than one of the standard loops then you
can also send asynchronous abort signals to a thread.