$ cat ex_NDBM_File_2.pl
use strict;
use warnings;
use Fcntl;
use NDBM_File;

tie(my %h, 'NDBM_File', 'ex_NDBM_File.ndbm', O_RDONLY, 0777) or die;

for my $k (sort keys %h) {
	print "$k --> '$h{$k}'\n";
}

$ perl ex_NDBM_File_2.pl
bar --> 'testing 12 .. hello, testing 12!'
foo --> '123 test'

##</code><code>##

$ cat ex_NDBM_File_1.pl
use strict;
use Fcntl;
use NDBM_File;

tie(my %h, 'NDBM_File', 'ex_NDBM_File.ndbm', O_RDWR|O_CREAT, 0777) or die;

$h{foo}='123 test';
$h{bar}='testing 12 .. hello, testing 12!';

$ perl ex_NDBM_File_1.pl

$