so using them is more problematic than other above-Unicode code points. Perl
invented an extension to UTF-8 to represent the ones above 2**36-1, so it is
likely that non-Perl languages will not be able to read files that contain
-these that written by the perl interpreter; nor would Perl understand files
+these; nor would Perl understand files
written by something that uses a different extension. For these reasons, there
is a separate set of flags that can warn and/or disallow these extremely high
code points, even if other above-Unicode ones are accepted. These are the