StandaloneCall = (C,A,L,L), SP, (ExplicitProcedureInvocation | ImplicitProcedureInvocation), [SP, (Y,I,E,L,D), SP, YieldItems] ;
YieldItems = (YieldItem, { [SP], ',', [SP], YieldItem })
| '-'
;
YieldItem = [ProcedureResultField, SP, (A,S), SP], Variable ;
ProcedureResultField = SymbolicName ;
Variable = SymbolicName ;