Add proposal to codify rules on matching brackets

All matched delimiters to should be determined by their
Unicode properties. I propose two simple rules to adopt
for uniformity, elegance and clarity.

v6d.pod

@@ -8,8 +8,8 @@ Plans for Perl 6 version 6.d
 
     Created: 09 Aug 2016
 
-    Last Modified: 09 Aug 2016
-    Version: 2
+    Last Modified: 16 Dec 2016
+    Version: 3
 
 This documents contains planned changes for v6.d, and who wants to do them.
 
@@ -70,5 +70,54 @@ Examples of this happening have showed up in the past.
 
 Jonathan Worthington
 
+=head1 Formal Rules for Defining Matched Delimiters/Brackets
+
+In v6.d we should formalize which brackets we support.
+How do we decide which delimiters should be added on future updates
+to the Unicode standard? We should look to the Unicode standard to help
+us define matching delimiters and brackets for Perl 6.
+
+All delimiters we support should conform to two simple rules for the sake of
+uniformity, elegance and clairity.
+
+=head2 Rules
+
+B<1.> Delimiter's Unicode General_Category must match one of these:
++ Pi -> Pf ( Punctuation, initial quote -> Punctuation, final quote)
++ Ps -> Pe (Punctuation, start -> Punctuation, end)
+
+B<2.> Are matched as either BidiBrackets or as BidiMirroring characters.
+
+Bidirectional brackets are specified
+L<here|http://www.unicode.org/Public/UCD/latest/ucd/BidiBrackets.txt>
+
+Non brackets have their matching glyph specified in this
+L<file|http://www.unicode.org/Public/UCD/latest/ucd/BidiMirroring.txt>
+
+=head2 Possible issues
+
+The only possible issue, is what to do with ornate parens.
+
+B<BidiBrackets.txt> states:
+
+“For legacy reasons, the characters U+FD3E ORNATE LEFT PARENTHESIS and
+U+FD3F ORNATE RIGHT PARENTHESIS do not mirror in bidirectional display
+and therefore B<do not form a bracket pair.>”
+
+In v6.c, roast includes tests for 'ornate left parens' and 'ornate right parens'
+for doing things like q[ ] type contructs and such. I think that we should not
+allow these parenthesis because firstly, Unicode states they do not form a matching pair
+of brackets. Secondly, the ornate parenthesis also do not have mirror glyphs.
+To make matters even worse, their Unicode general categories are the opposite of every
+matched bracket we support, the opening brackets tested for in v6.c open with
+"Pe"(End) and close with is "Ps"(Start).
+They break both of these proposed rules.
+
+In practice this is already implement with the exception of the ornate parenthesis,
+but I propose this be made an official part of the Perl 6 standard.
+
+=head2 Stakeholder
+
+Samantha McVey (samcv)
 
 =cut