perl 连接 mysql

use DBI;
my $database = 'xxx';
my $hostname = 'xxx';
my $port = '3720';
my $user = 'xxx';
my $password = 'xxx';
my $dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
my $dbh = DBI->connect($dsn,$user,$password);
?
my $sql = "select id from tbl_t";
my $sth = $dbh->prepare($sql);
$sth->execute();
while (my $ref = $sth->fetchrow_hashref())
{
??? my $myid = $ref->{'id'} ;
??? print $myid,"/n";
}

$dbh->disconnect();?exit; ???????????