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I'm almost tempted to call the first of these a bug: isn't '((x|y)*)*'
a perfectly valid (albeit somewhat redundant) regular expression? What
am I missing here?
Even if there are issues with capturing, shouldn't the version without
capturing subexpressions still work?
I get:
>>> re.compile(r'(?:(?:x|y)*)*')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/usr/lib/python2.5/re.py", line 180, in compile
 return _compile(pattern, flags)
 File "/usr/lib/python2.5/re.py", line 233, in _compile
 raise error, v # invalid expression
sre_constants.error: nothing to repeat