[Python-Dev] one last SRE headache

[Fredrik Lundh]

can anyone tell me how Perl treats this pattern?

    r'((((((((((a))))))))))\41'

in SRE, this is currently a couple of nested groups, surrounding
a single literal, followed by a back reference to the fourth group,
followed by a literal "1" (since there are less than 41 groups)

in PRE, it turns out that this is a syntax error; there's no group 41.

however, this test appears in the test suite under the section "all
test from perl", but they're commented out:

# Python does not have the same rules for \\41 so this is a syntax error
#    ('((((((((((a))))))))))\\41', 'aa', FAIL),
#    ('((((((((((a))))))))))\\41', 'a!', SUCCEED, 'found', 'a!'),

if I understand this correctly, Perl treats as an *octal* escape
(chr(041) == "!").

now, should I emulate PRE, Perl, or leave it as it is...

</F>

PS. in case anyone wondered why I haven't seen this before, it's
because I just discovered that the test suite masks syntax errors
under some circumstances...