Looks like this site can't handle Japanese as well :)
Anyway, I believe we can assume, that DBD::Oracle does not do any conversion, so the data obtained from the database comes in UTF-16 encoding, so it should be passed to the database in the same encoding.
Now, that's the goal. How to achieve it depends on what you are actually doing. I've already told you what you should do to use the obtained data in perl regular expressions. If you want to insert some Japanese text into database, then you would do something like this
my $data_to_be_inserted = Encode::encode("UTF-16", "Some Japanese text
I assume, we've clarified the issue with terminal output. If you have some other problems, then it is better to describe them in more detailed way, showing the code that does not work. Otherwise, I can only recommend you to read the documents mentioned in the very first answer to your post.