1# back references, ugh
2a\(b\)\2c bC        ESUBREG
3a\(b\1\)c bC        ESUBREG
4a\(b*\)c\1d         b         abbcbbd   abbcbbd   bb
5a\(b*\)c\1d         b         abbcbd
6a\(b*\)c\1d         b         abbcbbbd
7^\(.\)\1  b         abc
8a\([bc]\)\1d        b         abcdabbd  abbd      b
9a\(\([bc]\)\2\)*d   b         abbccd    abbccd
10a\(\([bc]\)\2\)*d   b         abbcbd
11# actually, this next one probably ought to fail, but the spec is unclear
12a\(\(b\)*\2\)*d               b         abbbd     abbbd
13# here is a case that no NFA implementation does right
14\(ab*\)[ab]*\1      b         ababaaa   ababaaa   a
15# check out normal matching in the presence of back refs
16\(a\)\1bcd          b         aabcd     aabcd
17\(a\)\1bc*d         b         aabcd     aabcd
18\(a\)\1bc*d         b         aabd      aabd
19\(a\)\1bc*d         b         aabcccd   aabcccd
20\(a\)\1bc*[ce]d     b         aabcccd   aabcccd
21^\(a\)\1b\(c\)*cd$  b         aabcccd   aabcccd
22