Forbid Bare C<\b> in Regexes

Implementation to close RT#128986

v6d.pod

@@ -127,4 +127,42 @@ a variable that defaults to C<42>.
 
 Zoffix Znet
 
+
+=head1 Forbid Bare C<\b> in Regexes
+
+=head2 Current Behaviour
+
+The backspace character is silently attempted to be matched:
+
+    $ perl6 -e 'say "foo" ~~ /"foo" \b/'
+    Nil
+    $ perl6 -e 'say "foo\b" ~~ /"foo" \b/'
+    ｢fo｣
+
+=head2 New Behaviour
+
+Attempting to use bare C<\b> in regexes will throw:
+
+    $ perl6 -e 'say "foo" ~~ /"foo" \b/'
+    ==SORRY==
+    Cannot use bare \b in regexes. For literal backspace use "\b",
+    for word boundaries use << or >> for left/right boundaries, respectively
+
+    $ perl6 -e 'say "foo\b" ~~ /"foo" "\b"/'
+    ｢fo｣
+
+=head2 Rationale
+
+It's very easy to accidentally use C<\b> for word boundaries, since that's
+the syntax in Perl/GNU/.NET regex. It's also uncommon to want to match
+a literal C<\b>, so requiring explicit quotes (or use of \c8 or \x8),
+is justifiable and won't be a burden.
+
+Implementing this will resolve
+L<RT#128986|https://rt.perl.org/Ticket/Display.html?id=128986>
+
+=head2 Steakholder
+
+Zoffix Znet
+
 =cut