Others have already explained how it works, but I would like to point out that this is not portable. It only works this way on machines that use ASCII (or a superset of ASCII, like ISO-8859-1) as their native character set. But Perl runs also on EBCIDIC platforms, which has a different character set, and ordering of the characters as ASCII has.

If HTML::Entities uses such a regex, then that's a bad thing.

Abigail