... you know that the "exit" return codes are from the exit command given to the Windows "cmd" display.

Duh ... a more accurate appraisal would be .. you should have realized that the "exit" return codes are from the exit command given to the Windows "cmd" display :-(
I needed to instead be looking at (eg):

D:\>perl -le "$x = 1; system perl, '-le', \"exit ($x)\"; print $?;"
256

D:\>perl -le "$x = 1; system perl, '-le', \"exit $x\"; print $?;"
256
[download]

Thanks roho !!

Cheers,
Rob