for my $chr (160 .. 255) {
    my $chr_byte = chr($chr);
    my $chr_utf8 = chr($chr); utf8::upgrade($chr_utf8);
    my $rx = qr{$chr_byte|X}i;
    print $chr . " " . ($chr_utf8 =~ $rx ? "ok" : "not ok") . "\n";
}