I am exceedingly interested in using this for my own purposes. I found the perlapi function that lets you figure this out. The type is, as I suspected, associated with the pad entry, not the variable. You can get it with XS via PadnameTYPE. It should be noted, though, that this function is not explicitly documented (i.e. not available in perlapi.pod), so it could change. But at least now you know how to get at it. :-)