chromatic: 11 wallclock secs (10.67 usr +  0.00 sys = 10.67 CPU) @ 46860.36/s (n=500000)
chromatic2: 10 wallclock secs ( 8.81 usr +  0.00 sys =  8.81 CPU) @ 56753.69/s (n=500000)
lookbehind: 10 wallclock secs ( 9.42 usr +  0.00 sys =  9.42 CPU) @ 53078.56/s (n=500000)
    substr:  4 wallclock secs ( 3.98 usr +  0.00 sys =  3.98 CPU) @ 125628.14/s (n=500000)