Benchmark: timing 100 iterations of with each, with keys...
 with each:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)
 with keys:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)
                          Rate with each with keys
with each 100000000000000000/s        --        0%
with keys 100000000000000000/s        0%        --