4 a\(b*\)c\1d b abbcbbd abbcbbd bb
8 a\([bc]\)\1d b abcdabbd abbd b
9 a\(\([bc]\)\2\)*d b abbccd abbccd
10 a\(\([bc]\)\2\)*d b abbcbd
11 # actually, this next one probably ought to fail, but the spec is unclear
12 a\(\(b\)*\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