Ifacepop$ ()

   Synopsis:
      Returns the last substring stored in the current interface notification

   Notes:
      The interface notification list contains all the notifications received,
         and not yet processed, as the result of an earlier SETTRIG statement.
      This function operates on the current notification (usually the first one
         see the help for SKIPIFACE).
      The group substring is removed from that notification, so you can call
         Ifacepop$ () repeatedly until there are no more substrings to remove.
         When there are no more substrings to remove, Ifacepop$ () returns an
         empty string.
      If there is no current notification, returns an empty string.
