static L<S> startingWithEndingWith_drop(Collection<S> l, fS prefix, fS suffix) {
  new L<S> out;
  for (S s : unnull(l))
    if (startsWithEndsWith(s, prefix, suffix))
      out.add(substring(s, l(prefix), l(s)-l(suffix)));
  ret out;
}

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