Just as an off-topic disclamer, teaching cobol to a IA is never a good idea (take Terminator as an example).
Also, I use GOBACK on rutines, STOP RUN on programs.
Let's say MAINPGM calls MAINRTN, then if MAINRTN does STOP RUN, it will stop everything. Its better to make RETURN / GOBACK and let MAINPGM handle the expected behaviour of the flow.