code: @Controller(events = EventType.MESSAGE, pattern = "^([a-z ]{2})(\\d+)([a-z ]{2})$")
      public void onReceiveMessage(WebSocketSession session, Event event, Matcher matcher) {
          reply(session, event, "First group: " + matcher.group(0) + "\n" +
                  "Second group: " + matcher.group(1) + "\n" +
                  "Third group: " + matcher.group(2) + "\n" +
                  "Fourth group: " + matcher.group(3));
      }
docs: Invoked when bot receives an event of type message with text satisfying
  the pattern {@code ([a-z ]{2})(\d+)([a-z ]{2})}. For example,
  messages like "ab12xy" or "ab2bc" etc will invoke this method.
  
  @param session
  @param event