Simplification of mark's first two problems:

Problem 1: looks like regex's negative look-head assertion is broken
>>> re.findall(r'(?!a)\w', 'abracadabra')
['b', 'r', 'c', 'd', 'b', 'r']
>>> regex.findall(r'(?!a)\w', 'abracadabra')
[]


Problem 2: in VERBOSE mode, regex appears to be ignoring spaces inside
character classes

>>> import re, regex
>>> pat = r'(\w)([- ]?)(\w{4})'
>>> for data in ['abbbb', 'a-bbbb', 'a bbbb']:
...    print re.compile(pat).findall(data), regex.compile(pat).findall(data)
...    print re.compile(pat, re.VERBOSE).findall(data),
regex.compile(pat,regex.
VERBOSE).findall(data)
...
[('a', '', 'bbbb')] [('a', '', 'bbbb')]
[('a', '', 'bbbb')] [('a', '', 'bbbb')]
[('a', '-', 'bbbb')] [('a', '-', 'bbbb')]
[('a', '-', 'bbbb')] [('a', '-', 'bbbb')]
[('a', ' ', 'bbbb')] [('a', ' ', 'bbbb')]
[('a', ' ', 'bbbb')] []

HTH,
John