Sample Code

Decision

Don't place decision to execute in the subroutine

perform get_start_end_date.

form get_start_end_date.

check not ( s_workdt[] is initial ).
...more processing...

endform.

instead do:

If not ( s_workdt[] is initial ).

perform get_start_end_date.

endif.

Case Statement

Use CASE statement instead of IF...ELSEIF when possible (It is only possible in equality tests)