Consider using DBI instead and running your SQL through Perl directly.

All your other questions seem to relate more on how to operate the sqlplus.exe program. Can you please explain where Perl is necessary for the operation?

Do you know how to run the sqlplus.exe program outside of Perl and get the results into a text file?

Also, "a few errors" is not something we can provide specific help on. Please tell us what you did, the exact error message and what you expect to happen instead.