use DBI;
use POE;

my $dbh = DBI->connect('dbi:mysql:****', '****', '****', {RaiseError => 1});

POE::Session->create(inline_states => {_start    => \&tester}, heap => {dbh => $dbh->clone()});
POE::Session->create(inline_states => {_start    => \&tester}, heap => {dbh => $dbh->clone()});

POE::Kernel->run();

sub tester {
    my $heap = $_[HEAP];
    for my $key (@{$heap->{dbh}->selectcol_arrayref("SELECT id, sleep(0.1) FROM mytable WHERE 1")}) {
        print $key;
    }
}