static S firstStartingWithIC_drop(Collection<S> l, fS prefix) {
  for (S s : unnull(l))
    if (swic(s, prefix))
      ret substring(s, l(prefix));
  null;
}

static S firstStartingWithIC_drop(S prefix, Collection<S> l) {
  ret firstStartingWithIC_drop(l, prefix);
}