anchor.diff:  ;
   
   sendStatementAsync :
  -	SEND TO (TOP | BOTTOM) identifier
  +	TO (TOP | BOTTOM) identifier
   	onExceptionClause?
   	notOnExceptionClause?
   ;
  
positive.code: ;
  
  acceptFromMnemonic :
  	ACCEPT identifier (FROM mnemonicName)?
  ;
  
  acceptMessageCount :
  	ACCEPT identifier MESSAGE? COUNT
  ;
  
  // add statement
  
negative.code: // perform statement
  
  performStatement :
  	PERFORM (performInlineStatement | performProcedureStatement)
  ;
  
  performInlineStatement :
  	performType? statement+ END_PERFORM
  ;
  
  performProcedureStatement :
  	procedureName ((THROUGH | THRU) procedureName)? performType?
  ;
  
  performType :
  	performTimes | performUntil | performVarying
  ;
  
  performTimes :
  