static ItIt<S> ai_dropLeadingPhrases(S s, Collection<S> phrases) {
  final Set<S> set = asCISet(phrases);
  L<S> tok = javaTokNPunctuation(s);
  ret notNulls_iterator(
    mapIterator(allTokSplits_nOnLeft_iterator(tok),
      func(Pair<LS> p) -> S {
        set.contains(trimJoin(simpleSpaces(p.a))) ? join(p.b) : null
      }));
}