Haven't worked with Japanese, but I have experienced Perl/Oraperl issues with
Oracle related to character sets.
My only advice would be to ensure that you have the following Oracle environment
settings set in your Perl environment prior to connecting
ORA_NLS
ORA_NLS33
NLS_LANG
this can be done via the following (your values will obviously differ)
$ENV{ORA_NLS}="/opt/oracle/product/8.1.7/migrate/nls/admin/data";
$ENV{ORA_NLS33}="/opt/oracle/product/8.1.7/migrate/nls/admin/data";
$ENV{NLS_LANG}="AMERICAN_AMERICA.US7ASCII";
Hope this is helpful...good luck!