I've done this, so I can answer :-)
in reply to connecting toOracle7 and Oracle9 simultaneously
The interface changed between Oracle v7 and v8. Version 8 compiles against oci8. The DBD::Oracle module compiles against the binaries, so you will need to have the Oracle client software installed on each machine you want to run your script from. The server is licensed, the client is not, so it can be installed where ever you want as long as you don't build a database there. You cannot compile the module for v8 and copy it to machine with v7.
When you compile the module against your 9.2.x.x libraries you will be able to connect to the 7.x.x database. Connecting to two databases at the same time, even in same script should not be a problem, I've done this for a dataload in the past.
Your standard oracle environment variables should be set:
If you have problems connecting to the v7 from the v9 host, check your tnsnames.ora file to see if the entries have SERVICE names instead of SID entries.
- ORACLE_HOME: where you installed the oracle binaries
- TNS_ADMIN: if your tnsnames.ora and sqlnet.ora files are located somewhere non-standard
I think that's about it, off the top of my head. Good luck!