...
$dbh = DBI->connect("DBI:mysql:$database:$hostname", $user, $password);
$statement = "select ... order by ...";
$sth = $dbh->prepare($statement)
                or die "Can't prepare $statement: $dbh->errstr\n";
$rv = $sth->execute
                or die "can't execute the query: $sth->errstr\n";
my @row;
while(@row = $sth->fetchrow_array) {
  # @row contains the individual columns
  # ... do work ...
}

$rc = $sth->finish;
$rc = $dbh->disconnect;