anchor.diff:  fragment Y:('y'|'Y');
   fragment Z:('z'|'Z');
   
  +COMMENT
  +    : ';' ~[\r\n]* ->skip
  +    ;
  +
   CR
       : '\n'
       ;
  
positive.code:     | (term (LT | GT | EQUALS) term)
      ;
  
  comment
      : SEMICOLON ~(CR)*
      ;
  
  identifier
      : IDENTIFIER
      ;
  
negative.code: subproc
      : identifier (LPAREN paramlist? RPAREN)? (SPACE* command)+
      ;
  
  command
      : set_
      | for_
  