Forgot one really fun aspect of old Fortran. It was call by reference, with the following fun result:

    ....
    CALL MUNG(2)
    I = J + 2
    ...
    SUBROUTINE MUNG(N)
    N = 42
    RETURN
    END

After passing the constant 2 to MUNG, later uses of 2 will actually give you the value 42. Have fun debugging that!