Benchmark: timing 1000000 iterations of grep, index...
     grep: 11 wallclock secs (10.22 usr +  0.00 sys = 10.22 CPU) @ 97895.25/s (n=1000000)
     index:  2 wallclock secs ( 2.28 usr +  0.00 sys =  2.28 CPU) @ 438020.15/s (n=1000000)