RLH 2006-09-26: That is sad. Nick was always very helpful.
AMG: Not to take anything away from Nick, but the linked article and its comments attribute the development of Tk itself to Nick. Sample quote: "Tk was initially born out of frustration that perl didn't have a native GUI at the time. Nick tirelessly developed Tk for over a decade." Tcl isn't mentioned even once in the article or its comments.
I guess the charitable interpretation is that "Tk" is meant as the name of the Perl module which he did develop, not the like-named GUI toolkit with which it interfaces.
PYK 2014-04-02: According to the Perl page, though, he did actually hack on Tk itself quite a bit, producing a fork that didn't require Tcl, which was then used by Perl/Tk. Also, in the article, "Tk" refers to the Perl module.