Benchmark: timing 100000 iterations of do, sys...
        do:  4 wallclock secs ( 2.91 usr +  0.82 sys =  3.73 CPU) @ 26809.65/s (n=100000)
       sys: 441 wallclock secs ( 1.65 usr 19.06 sys + 304.06 cusr 117.50 csys = 442.27 CPU) @ 226.11/s (n=100000)