use strict;
use MLDBM qw(DB_File);
use DB_File;
use Data::Dumper ();
use Fcntl qw(O_RDWR O_CREAT);

my $r = shift;
$r->send_http_header("text/plain");

my $rh = {
          bar => ['a'..'c'],
          tar => { map {$_ => $_**2 } 1..4 },
         };

my $dbfile = "/tmp/foo.db";
tie my %dbm, 'MLDBM', $dbfile, O_RDWR|O_CREAT, 
    0600, $DB_HASH or die $!;
# assign a reference to a Perl datastructure
$dbm{foo} = $rh;
untie %dbm;

# read the assigned value
tie %dbm, 'MLDBM', $dbfile, O_RDWR|O_CREAT, 
    0600, $DB_HASH or die $!;
my $foo = exists $dbm{foo} ? $dbm{foo} : 'undefined';
untie %dbm;

print Data::Dumper::Dumper($foo);