This is a application-wide thing that you can access statically from anywhere.
You register a history listener and it gets an onChange() event
notification.
Within the application, Hyperlinks() add a history item to the stack
and, since the current item changes, the onChange() event fires.
When the onChange() event fires, you retrieve the historyToken
and use this to set your application up the way you want it. Anything from getting the
token 'Home' and showing the Home Page, to more complicated things. This page has
the token "Listeners~HistoryListener" and so the app splits it up on "~" and goes to
the Listeners tab in the main menu and then to the HistoryListener tab on this menu.