Comment 1 for bug 234224

It looks like they are running from sources and their installation is incomplete and missing the msgcat package.
I do:
    uplevel #0 namespace import ::msgcat::mc
which defines the 'mc' command at the global namespace. msgcat is an integrated part in Tcl.
Maybe it is better to advice people to run from one of single xecutable tclkits instead. They can be found as usual here: http://www.equi4.com/tclkit/download.html