First, check CPAN to see what the current version of Tk is. At the time of this response, it's 804.028, so it's possible that your bug has been fixed. You can check the Tk bug queue to see the state of reported bugs, although I don't know if your specific one was ever entered in the queue. You can also check the Changes file for the release to see if your issue is mentioned there.
If you don't see anything specific, you might note that the author of your quoted message is the maintainer of Tk, so it's likely that the patch has been applied. :)
Tk is a distribution. You can't upgrade individual modules.
Check the Perl/Platform Version Matrix to see which versions of Tk work on which platforms and under what versions of Perl.
If you absolutely must apply just this one change, download the source for the version of Tk you're using, apply the patch, and rebuild it.