#!/usr/bin/perl -w 
use strict;
use DBI;

# connect to the database and create a handle to the connection.
my $dbh=DBI->connect('DBI:mysql:host=myhost.domain.tld;database=mydatabase',
                         'user','password')
       or die $DBI::errstr;

#create a statement handle and prep our SQL
my $sth=$dbh->prepare(qq(
select user_id,username,password,given,surname from users_table order by user_id
)) or die $dbh->errstr;

$sth->execute();
while (my $row=$sth->fetchrow_arrayref){
        # do something with it
}

| rest of code