#!/usr/bin/perl
use strict;
use warnings;
use DBI;

my $dsn = "DBI:mysql:host=somehost;database=db-you-want";
my $dbh = DBI->connect($dsn,"user","password") or die "Couldn't connect: " . DBI->errstr();

my $query = "SELECT somestuff FROM sometable WHERE somefield='something';
my $sth = $dbh->do($query);
while(my $somestuff = $sth->fetchrow()) {
     # do something interesting ...
}
$sth->finish();
$dbh->disconnect();