[Python-Dev] one last SRE headache

[Tim Peters]

> Suggestion:
>
> If there are fewer than 3 digits, it's a group.

Unless it begins with a 0 (that's what's documented today -- read the docs
<wink>).

> If there are exactly 3 digits and you have 100 or more groups, it's a
> group -- too bad, you lose octal number support.  Use \x. :-)

The docs say you can't use backreferences for groups higher than 99.

> If there are exactly 3 digits and you have at most 99 groups, it's an
> octal escape.

If we make the meaning depend on the number of preceding groups, we may as
well emulate *all* of Perl's ugliness here.