use AnyDBM_File;
*****
@AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File);
*****
use GDBM_File;
*****
use Fcntl;         # for O_* values
use NDBM_File;
use DB_File;
tie %oldhash, "NDBM_File", $old_filename, O_RDWR|O_EXCL, 0644;
tie %newhash, "DB_File",   $new_filename, O_CREAT|O_RDWR;
while (($key,$val) = each %oldhash) {
    $newhash{$key} = $val;
}