The easiest way is to do this is probably :-

my $dbh=DBI->connect(.....);
my $query = "INSERT INTO subjects VALUES (?)"; 
my $sth=dbh->prepare($query);

foreach my $subject (split /\0/,$form{'subject'}) {
     $rv  = $sth->execute($subject);
}
$sth->finish();
$dbh->disconnect();
[download]

Hope this helps
UnderMine