-Instead of assigning to an implicit lexical C<$_>, C<given> now makes the
-global C<$_> an alias for its argument, just like C<foreach>. However, it
-still uses lexical C<$_> if there is lexical C<$_> in scope (again, just like
-C<foreach>) [perl #114020].
+=head2 New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes
+
+Unicode has now withdrawn their previous recommendation for regular
+expressions to automatically handle cases where a single character can
+match multiple characters case-insensitively; for example, the letter
+LATIN SMALL LETTER SHARP S and the sequence C<ss>. This is because
+it turns out to be impracticable to do this correctly in all
+circumstances. Because Perl has tried to do this as best it can, it
+will continue to do so. (We are considering an option to turn it off.)
+However, a new restriction is being added on such matches when they
+occur in [bracketed] character classes. People were specifying
+things such as C</[\0-\xff]/i>, and being surprised that it matches the
+two character sequence C<ss> (since LATIN SMALL LETTER SHARP S occurs in
+this range). This behavior is also inconsistent with the using a
+property instead of a range: C<\p{Block=Latin1}> also includes LATIN
+SMALL LETTER SHARP S, but C</[\p{Block=Latin1}]/i> does not match C<ss>.
+The new rule is that for there to be a multi-character case-insensitive
+match within a bracketed character class, the character must be
+explicitly listed, and not as an end point of a range. This more
+closely obeys the Principle of Least Astonishment. See
+L<perlrecharclass/Bracketed Character Classes>. Note that a bug [perl
+#89774], now fixed as part of this change, prevented the previous
+behavior from working fully.
+
+=head2 Change to Warnings About Lexical Subroutines
+
+The warnings category for lexical subroutines is now
+"experimental::lexical_subs", with two colons, not
+"experimental:lexical_subs";
https://perl5.git.perl.org / perl5.git / blobdiff