which is much more efficient. (Yves Orton)
+=item Vertical and horizontal whitespace, and linebreak
+
+Regular expressions now recognize the C<\v> and C<\h> escapes, that match
+vertical and horizontal whitespace, respectively. C<\V> and C<\H>
+logically match their complements.
+
+C<\R> matches a generic linebreak, that is, horizontal whitespace, plus
+the multi-character sequence C<"\x0D\x0A">.
+
=back
=head2 The C<_> prototype