anchor.diff:  
   callByReferenceStatement :
   	(BY? REFERENCE)? (identifier | ADDRESS OF identifier | fileName)+ 
  +;
  +
  +callByValueStatement :
  +	BY? VALUE identifier+ 
   ;
   
   callByContentStatement :
  
positive.code: callStatement :
  	CALL (identifier | literal)
  	(
  		USING (callByReferenceStatement | callByContentStatement)+
  	)?
  	(ON? OVERFLOW statements)?
  	onExceptionClause?
  
negative.code: ;
  
  programName :
  	cobolWord | NONNUMERICLITERAL
  ;
  
  qualifiedDataName :
  