static L<S> startingWithICTrim_drop(Collection<S> l, fS prefix) {
  new L<S> out;
  for (S s : unnull(l))
    if (swic(s, prefix))
      out.add(trimSubstring(s, l(prefix)));
  ret out;
}

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