# creating a dummy db first
use DB_File;
tie my %h, "DB_File", "/tmp/test.db";
$h{foo} = "bar";
untie %h;

# now trying to read it
use BerkeleyDB;
my $db = new BerkeleyDB::Hash
   -Env => BerkeleyDB::Env->new(-Home => "/tmp"),
   -Filename => "test.db"
or die "could not open database";