One more thing I just noticed that I really can't explain:

Looking at Activity Monitor, Robert Purves' tiny app only has 1 thread,
while mine has 2. His uses a tiny bit of CPU time, while mine is around 22%
and climbing. His also shows a steady RSIZE, while mine keeps climbing, even
the version that uses a function call instead of a GOSUB.

As far as I know, I haven't done anything to create a second thread, is that
something the FB compiler can do on its own?!?

Seems to me the ultimate answer probably lies in that second thread.

- John