static PrefixSuffixAndEntries autoDeprefixAndSuffix(Cl<S> l) {
  new PrefixSuffixAndEntries out;
  out.prefix = commonPrefixMulti(l);
  LS l2 = lambdaMap_curry dropPrefix(out.prefix, l);
  out.suffix = commonSuffixMulti(l2);
  if (empty(out.prefix) && empty(out.suffix)) null;
  out.entries = lambdaMap_curry dropSuffix(out.suffix, l2);
  ret out;
}