Read the Unicode chapter in the DBD::Oracle documentation, it explains exactly what has to be done to read and write Oracle Data as UTF-8. Make sure that other I/O from and to perl is also UTF-8, so your strings contain unicode characters (utf8 flag on) and not bytes representing a random unicode encoding (utf8 flag off). See also the tests t/40UnicodeRoundTrip.t and t/41Unicode.t in DBD::ODBC for some basic examples.

Alexander