$dbh->do("DECLARE csr CURSOR WITH HOLD FOR SELECT * FROM large_table order by id");
while (1) {
    my $sth = $dbh->prepare("fetch 100000 from csr");
    $sth->execute;
    my $res = $sth->fetchall_arrayref({});
    if ($res && @{$res}) {
        # batch process the 100k rows
    } else {
        # error or no more rows
        exit;
    }
}