Function 4Dh            Get Child-Program Return Value

    Retrieves the return value specified by the last child program.
    The child program must have specified a return value by using
    either function 4ch (EXIT) or 31h (KEEP).

        Entry   AH = 4Dh

        Return  AL = Return value from child program
                AH = Termination method
                     | 00h   Normal termination
                     | 01h   Terminated by Ctrl-C (Ctrl-Break)
                     | 02h   Terminated by DOS because of
                     |       critical device error
                     | 03h   Terminated by function 31h

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    Note
    The return value for the program is available only once.
    Subsequent calls to this function in relation to the same child
    program give meaningless results.

    If there is no child-program return value to retrieve, this
    function does not return an error, and the information in the AX
    register is meaningless.