The re module throws an exception for re.compile(r'[\A\w]'). latest
regex doesn't, but I don't think the pattern is matching correctly.
Shouldn't findall(r'[\A]\w', 'a b c') return ['a'] and
findall(r'[\A\s]\w', 'a b c') return ['a', ' b', ' c'] ?

Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import re
>>> for s in [r'\A\w', r'[\A]\w', r'[\A\s]\w']: print re.findall(s, 'a b c')
...
['a']
[]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/re.py", line 177, in findall
    return _compile(pattern, flags).findall(string)
  File "/usr/lib/python2.6/re.py", line 245, in _compile
    raise error, v # invalid expression
sre_constants.error: internal: unsupported set operator
>>> import regex
>>> for s in [r'\A\w', r'[\A]\w', r'[\A\s]\w']: print regex.findall(s, 'a b c')
...
['a']
[]
[' b', ' c']