Oracle has no issues with multiple statements per session, so there is something else going on. Opening and closing the connection each time is seriously wasteful. I would first off suggest that you:

• display the $query statements via STDOUT to verify they are correctly formed
• throw an error message on an unsuccesful execution
• I don't see any "my"'s in there, so I assuming you are not using "use strict", you want to do that.

I also love the suggestion to use the native DBI Oracle drivers rather than ODBC. you may want to do one commit (depnding on your oracle defaults) after the loop after determining all has gone well.

good luck