use DBI;
use strict;
use warnings;

my $dbh = DBI->connect('dbi:mysql:test','root','',{RaiseError => 1})
  or die;
my $sth = $dbh->prepare('select sum(x) from dummy');
$sth->execute();
while(my @val = $sth->fetchrow_array()) {
   print "$val[0]\n";
}