...
my $path = U2A("some-path-in-japanese-CP932");

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