sub make_sorter {
  my $order = shift;
  return sub { by_list( $order ) };
}
my $order1 = make_sorter( [ qw( a c d e b f ) ] );
my $order2 = make_sorter( [ qw( f b a d c e ) ] );
my @order1 = sort $order1, @tobesorted;
my @order2 = sort $order2, @tobesorted;
my @other2 = sort $order2, @othertobesorted;