RXFNCCAL processes calls to external functions.
When called: When REXX calls an external subroutine or function.
Default action: Call the external routine using the usual external function search order.
Exit Action: Call the external routine, if possible.
Continuation: If necessary, raise REXX error 40 ("Incorrect call to routine"), 43 ("Routine not found"), or 44 ("Function or message did not return data").