code: private static void startProperty( String name, Properties props, Stack<String> stack )
      {
          String propValue = System.getProperty( name );
          if( propValue == null )
          {
              propValue = props.getProperty( name );
          }
          if( propValue == null )
          {
              push( stack, "${" + name + "}" );
          }
          else
          {
              push( stack, propValue );
          }
      }
docs: Starts a new property.
  
  @param name  The name of the property.
  @param props The Properties we are exchanging with.
  @param stack The parsing stack.