> These features are to bring the Regexp code closer in line with Perl 5.10

Why 5.1 instead of 5.8 or at least 5.6?  Is it just a scope-creep issue?

> as well as add a few python-specific

because this also adds to the scope.


> 2) Make named matches direct attributes 
> of the match object; i.e. instead of m.group('foo'), 
> one will be able to write simply m.foo.

> 3) (maybe) make Match objects subscriptable, such 
> that m[n] is equivalent to m.group(n) and allow slicing.

(2) and (3) would both be nice, but I'm not sure it makes sense to do 
*both* instead of picking one.

> 5) Add a well-formed, python-specific comment modifier, 
> e.g. (?P#...);  

[handles parens in comments without turning on verbose, but is slower]

Why?  It adds another incompatibility, so it has to be very useful or 
clear.  What exactly is the advantage over just turning on verbose?

> 9) C-Engine speed-ups. ...
> a number of Macros are being eliminated where appropriate.

Be careful on those, particular on str/unicode and different compile options.