+=item C<\b{lb}>
+
+This matches according to the default Unicode Line Breaking Algorithm
+(L<http://www.unicode.org/reports/tr14/>), as customized in that
+document
+(L<Example 7 of revision 35|http://www.unicode.org/reports/tr14/tr14-35.html#Example7>)
+for better handling of numeric expressions.
+
+This is suitable for many purposes, but the L<Unicode::LineBreak> module
+is available on CPAN that provides many more features, including
+customization.
+
+=item C<\b{sb}>
+
+This matches a Unicode "Sentence Boundary". This is an aid to parsing
+natural language sentences. It gives good, but imperfect results. For
+example, it thinks that "Mr. Smith" is two sentences. More details are
+at L<http://www.unicode.org/reports/tr29/>. Note also that it thinks
+that anything matching L</\R> (except form feed and vertical tab) is a
+sentence boundary. C<\b{sb}> works with text designed for
+word-processors which wrap lines
+automatically for display, but hard-coded line boundaries are considered
+to be essentially the ends of text blocks (paragraphs really), and hence
+the ends of sententces. C<\b{sb}> doesn't do well with text containing
+embedded newlines, like the source text of the document you are reading.
+Such text needs to be preprocessed to get rid of the line separators
+before looking for sentence boundaries. Some people view this as a bug
+in the Unicode standard, and this behavior is quite subject to change in
+future Perl versions.
+