input: 40 x 'a' + '!'   budget 1000 ms
vulnerable   (?:(?:a+)+)+b    ABORTED after 1019 ms
rewritten    a+b              0 ms  matches=false
possessive   (?:a++)++b       7 ms  matches=false
atomic       (?>(?:a+)+)b     0 ms  matches=false

find() a+b        n=5000    139 ms  found=false
find() a+b        n=10000   489 ms  found=false
find() a+b        n=20000  1906 ms  found=false
find() (?<!a)a+b  n=5000      6 ms  found=false
find() (?<!a)a+b  n=10000     6 ms  found=false
find() (?<!a)a+b  n=20000    15 ms  found=false