IFACESTRINGS ()

   Synopsis:
      Returns the number of substrings 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.
      If the list is empty, -1 is returned. If the trigger's pattern did not
         contain substrings (backreferences), 0 is returned.
