use Encoding;

sub U2A { return encode('cp932', shift) }

my $path = "some-path-in-japanese-CP932";

if (-d U2A($path)) {
    chdir U2A($path);
    my $tmpfile = "some-name-in-CP932";
    system(U2A("some_cmd \"other-filename-in-CP932\" $tmpfile"));
    unlink U2A($tmpfile) if !-s U2A($tmpfile);
    # etc...
}