use Fcntl;
use DB_File;

my $db_file = '/tmp/db_file';
unlink $db_file if -e $db_file;

my $btree_info = new DB_File::BTREEINFO;
$btree_info->{'flags'} = R_DUP;

my $comparison_type = shift @ARGV;
if (! $comparison_type) {
	# this method works
	$btree_info->{'compare'} = sub  { my($a,$b) = @_; $a <=> $b };
} else {
	# this method does not work
	$btree_info->{'compare'} = sub  { $_->[0] <=> $_->[1] };
}

$tied_hash_obj = tie( %tied_hash, 'DB_File', $db_file, O_RDWR|O_CREAT, 0640, $btree_info )
	or die "Can't tie tied_hash to $db_file: $!";


for ( 0 .. 20) {
	$tied_hash{rand(100)} = ++$i;
}

my ($status, $k, $v);
for (
	$status = $tied_hash_obj->seq($k, $v, R_FIRST);
	$status == 0;
	$status = $tied_hash_obj->seq($k,$v, R_NEXT)
	) {
	push @vals_sorted_by_keys, $v;
	push @sorted_keys, $k;
}

print join("\n", @vals_sorted_by_keys),"\n********\n";
print join("\n", @sorted_keys),"\n";