static ItIt<S> ai_dropTrailingPhrases_repeat(S s, Collection<S> phrases) {
  final Set<S> set = asCISet(phrases);
  
  final new HashSet<S> seen;
  
  // Make pool of iterators
  final L<Iterator<S>> pool = ll_linkedList((Iterator<S>) ai_dropTrailingPhrases(s, set));
  ret iteratorFromFunction(func -> S {
    while ping (!empty(pool)) {
      Iterator<S> it = first(pool);
      if (!it.hasNext()) continue with removeFirst(pool);
      
      // Get entry and check if seen already
      S entry = it.next();
      if (!seen.add(entry)) continue;

      // found new entry - return and schedule for further analysis
      pool.add(ai_dropTrailingPhrases(entry, set));
      ret entry;
    }
    null;
  });
}

Began life as a copy of #1018115