Re: RFC 150 (v1) Extend regex syntax to provide for return of a hash of matched subpatterns

(This thread has been inactive for a while.  See 
http://www.mail-archive.com/[email protected]/index.html#0 
0015 for it's short history.)

Long ago Tom Christiansen wrote:

>This is useful in that it would stop being number dependent.
>For example, you can't now safely say
>
>    /$var (foo) \1/
>
>and guarantee for arbitrary contents of $var that your you have
>the right number backref anymore.
>
>If I recall correctly, the Python folks addressed this.  One
>might check that.

Python does, indeed, have something similar.  See (?P...) and 
(?P=...) at http://www.python.org/doc/current/lib/re-syntax.html .

Tom's comment points out a shortcoming in the original RFC:  There's 
no way to make, by name, a backref to a named group.  I propose to 
fix that in a revised version of RFC 150.  I don't have strong 
feelings about what the syntax should be.  Here one idea:

   The substring matched by (?%some_name: ... ) can be referred to as 
$%{some_name}.

That's kind of ugly, so other suggestions are welcome.  (The idea was 
to do something analogous to $1, $2, etc.  Unfortunately ${some_name} 
is already taken.  Maybe $_{some_name} would also work -- though if 
%_ seems too valuable to use for this limited purpose.)