| Subject: | FFFF is not the end of Unicode |
The documentation mentions FFFF several times, and the code contains
constructs like [\da-fA-F]{1,4}.
There exist Unicode codepoints up to U+10FFFF, and Perl can safely deal
with characters up to "\x{ffffffff}", possibly even longer depending on
compile-time options.
Relax the restrictions, update the documentation.