anchor.diff:  
   anon
       : OPEN_SQUARE_BRACKET CLOSE_SQUARE_BRACKET
  -    ;	
  +    ;
   // $>
   
   // $<Lexer
  
positive.code:     ;
  
  varOrTerm
      : var | graphTerm
      ;
  
  varOrIRIref
  
negative.code:     ;
      
  modify
      : ( WITH iriRef )? (deleteClause insertClause? | insertClause) usingClause* WHERE groupGraphPattern -> ^(MODIFY ^(WITH iriRef)? deleteClause* insertClause* usingClause* ^(WHERE groupGraphPattern))
      ;
    
  deleteClause
  