sub contains {
  my ($s, $t) = @_;
  my (%sc, %tc);
  for (split('', $s)) { $sc{$_}++ };
  for (split('', $t)) { $tc($_}++ };
  for my $k (keys %sc) {
    return 0 unless $sc{$k} <= $tc{$k};
  }
  1;
}