Benchmark: timing 1 iterations of list, ref...
      list: -1 wallclock secs ( 0.14 usr +  0.00 sys =  0.14 CPU) @  7.09/s (n=1
)
            (warning: too few iterations for a reliable count)
       ref:  0 wallclock secs ( 0.14 usr +  0.00 sys =  0.14 CPU) @  7.09/s (n=1
)
            (warning: too few iterations for a reliable count)
2000001000000
2000001000000