Beginning in Peek/Spy Version 4.6, more than one watcher is allowed
   to watch the same terminal, all at the same time.

   The first watcher who starts watching a particular terminal is
   designated the primary watcher.

   Any and all additional watchers who then start watching that same
   terminal are designated secondary watchers.

   A primary watcher has all of the normal Peek/Spy capabilities and
   hot-keys etc which a Peek/Spy watcher has always had in the past.

   Secondary watchers are passive. They may watch and end watching, but
   other hot-keys are disabled and keyboard control is not usually
   allowed, except via PERMIT_INPUT and REQUEST_INPUT. (See the
   top-level PEEK Subtopic: Permit-Input|Request-Input.)

   If there are additional (secondary) watchers also watching when a
   primary watcher ends watching, then the earliest secondary watcher
   becomes the new primary watcher.

   Any hot-keys, keyboard control, etc, which were disabled for the
   watcher as a secondary watcher, become functional when a secondary
   watcher becomes the new primary watcher.