Benchmark: timing 5000000 iterations of index, regex...
     index:  1 wallclock secs ( 1.10 usr +  0.00 sys =  1.10 CPU) @ 4545454.55/s (n=5000000)
     regex:  2 wallclock secs ( 2.25 usr +  0.01 sys =  2.26 CPU) @ 2212389.38/s (n=5000000)
Benchmark: timing 5000000 iterations of index, regex...
     index:  4 wallclock secs ( 2.99 usr +  0.01 sys =  3.00 CPU) @ 1666666.67/s (n=5000000)
     regex:  3 wallclock secs ( 3.66 usr +  0.01 sys =  3.67 CPU) @ 1362397.82/s (n=5000000)