code: private int parseSimpleForClause() throws TTXPathException {
  
          consume("for", true);
  
          int forCondNo = 0;
  
          // parse all conditions and count them
          do {
  
              consume(TokenType.DOLLAR, true);
  
              // parse for variables
              final String varName = parseVarName();
              consume("in", true);
  
              parseExprSingle();
              mPipeBuilder.addVariableExpr(getTransaction(), varName);
              forCondNo++;
  
          } while (is(TokenType.COMMA, true));
  
          return forCondNo;
  
      }
docs: Parses the the rule SimpleForClause according to the following production
  rule:
  <p>
  [5] SimpleForClause ::= <"for" "$"> VarName "in" ExprSingle ("," "$" VarName "in" ExprSingle)* .
  </p>
  
  @return returns the number of for-conditions
  @throws TTXPathException