I think this was the first line of the forth in the library of an older version of jonesforth (https://rwmj.wordpress.com/2010/08/07/jonesforth-git-reposit...), but now I can only find it in my port:

  : \ IMMEDIATE
        #IB @ >IN !
  ; \ We can now comment!

Implementing a forth system is unbelievably fun because of gems like this.