Having run the 'make test TEST_VERBOSE=1' on several different platforms and not getting the error, also checking the error level once the 'make test' was done (echo %ERRORLEVEL% / echo $?) on those platforms and seeing it '0' in all cases and reading the 'perldoc -f exit' and seeing that "If EXPR is omitted, exits with 0 status.", I thought the 'exit' command I already had in my test covered that.

I suppose I could modify my 'exit' with 'exit 0'.

That still doesn't answer what the "Dubious, test returned 5 (wstat 1280, 0x500)" means. I'm guessing the 0x500 is the '5', but what is the 'wstat 1280'? Googling seems to indicate it has something to do with parent/child processes. There is no test that returns 5 in my test program and I figured the line "All 3 subtests passed" in the log was a good thing.