Benchmark: timing 5000000 iterations of index, regex...
     index:  2 wallclock secs ( 1.04 usr +  0.00 sys =  1.04 CPU) @ 4807692.31/s (n=5000000)
     regex:  2 wallclock secs ( 2.16 usr +  0.01 sys =  2.17 CPU) @ 2304147.47/s (n=5000000)
Benchmark: timing 5000000 iterations of index, regex...
     index:  3 wallclock secs ( 2.83 usr +  0.00 sys =  2.83 CPU) @ 1766784.45/s (n=5000000)
     regex:  4 wallclock secs ( 3.45 usr +  0.02 sys =  3.47 CPU) @ 1440922.19/s (n=5000000)