Further to this, I made a post on Cygwin's mailing list. http://www.cygwin.com/ml/cygwin/2007-10/threads.html#00206 ..apparently Tcllib is not part of the standard tcl library, its something different. I am only getting started with Tcl/Tk so forgive the misunderstanding. So my excercise may actually be to find Tcllib and compile it for cygwin.