(illegal example)
(Define rs274-style sub before numeric O-word main program end)
O1 (main program begin)
G0 X1Y2
(calling sub 2)
O2 call
(returned from sub 2)

(Illegal:  O-sub with no M02 or M30 terminating main)
O2 sub (subprogram begin)
(in sub 2)
G0 Z3
(returning from sub 2)
O2 endsub
