FILTER_ONLY regex => sub { s/\\s/[\\s\xA0]/g };

##</code><code>##

print "\xA0" =~ /[A-Z\s]/ ? "Yay!\n" : "Hmmm\n";
print '[]'   !~ /[A-Z\s]/ ? "Yay!\n" : "Hmmm\n";