Well, I guess I was asleep at the wheel, or some such... I really didn't notice what the system was telling me, earlier in processing.

I made a simple, dumb, mistake: I copied my .xs file into the extension subdirectory and then ran h2xs -b5.6.1 -Oxan CLIEXT, which just happens to create the file CLIEXT.xs, which then overwrote mine.

So, no enableUser routine was defined and attempts to use it of course failed.

Sorry about the "noise", but on the other hand, this may help some other novice XS programmer. ;)

The moral, if you have an existing XS file, copy it in to the extension directory last.

Bob