if-statement =

  -----> IF predicate THEN --+-> compound-use-statement -+--------+
                             +------------ <-------------+        |
  +---------------------------------------------------------------+
  ++-+--------------------------------------------------------+-+-+
   | +-> ELSEIF predicate THEN -+-> compound-use-statement -+-+ | |
   |                            +------------ <-------------+   | |
   +---------------------------- <------------------------------+ |
  +---------------------------------------------------------------+
  +--+----------------------------------------+--> END IF --------->
     +-> ELSE --+-> compound-use-statement -+-+
                +------------ <-------------+