If my memory serves me correctly, when you use PPM to install DBD-Oracle, it prompts you to download a complete set of Oracle client drivers and then sets them up under the Perl root somewhere, but I could be confusing that with something else. One important thing in your Perl code is to set $ENV{ORACLE_HOME} before you try to use DBI->connect to open an Oracle connection. Your co-worker may be right as well. I don't have my work machine in front of me so I can't tell you offhand, but basically you may want to re-run the Oracle Installer and make sure you've selected all the options for client-side drivers.