Benchmark: timing 1 iterations of list, ref...
      list:  1 wallclock secs ( 0.36 usr +  0.11 sys =  0.47 CPU) @  2.13/s (n=1
)
            (warning: too few iterations for a reliable count)
       ref:  0 wallclock secs ( 0.11 usr +  0.00 sys =  0.11 CPU) @  9.17/s (n=1
)
            (warning: too few iterations for a reliable count)