The best thing you can do to optimize your performance is to a) design the SCHEMA to best support the kinds of queries you want to make, including making sure to index the right columns and b) phrase your queries in the best way - which you should be able to tell with Oracle's own tools (EXPLAIN, or whatever they call the SQL command that optimizes and summarizes queries) c) make sure you are using DBI placeholders and looping correctly to minimize multiple prepares d) use bind_cols and/or the array fetches

Unless your Perl is quite invovled, it's unlikely that anything else will have anywhere as much impact as those things.