Thanks for the feedback everyone.
Andrew and David, I did look at those pages, but I couldn't find any pure tcl code that does diffs. The 'diffs in TCL' page is outdated. I think all of that code is now in tcllib and that's the code that my proc uses. AFAIK, the Tcl'ers Wiki runs tkdiff to do the diffs and I didn't want to have to install Tk. The link to Pascal Scheffer's code 404's, but I think he uses the CVS diff function.
Malte and Nick, I'd be happy to place this in acs-tcl. Maybe as util::diff? I also don't have CVS commit access anymore, so either someone could restore that (username was vinodk) or I'd be happy to mail the patch to someone who could commit it.
