use CDB_File;

    $t = new CDB_File ('t.cdb', "t.$$") or die ...;
    $t->insert('key', 'value');
    $t->finish;

##</code><code>##

    use CDB_File;

    tie %data, 'CDB_File', $filename or
            die "$0: can't tie to $filename: $!\n";

    if (defined $data{}) {
      # ...
    }