use Rose::DB;

Rose::DB->register_db
(
  domain => 'default',
  type   => 'default',
  driver => 'Pg',
);

$db = Rose::DB->new;

$s = '{2,"four",6,8}';
$a = $db->parse_array($s);

pop(@$a);
$a->[2]++;

$f = $db->format_array($a); # '{2,"four",7}'