code: private void parseVarRef() {
  
          consume(TokenType.DOLLAR, true);
          final String varName = parseVarName();
          mPipeBuilder.addVarRefExpr(getTransaction(), varName);
      }
docs: Parses the the rule VarRef according to the following production rule:
  <p>
  [44] VarRef ::= "$" VarName .
  </p>