Benchmark: timing 50000 iterations of Fn, Hash, HashRef...
       Fn: 28 wallclock secs (27.56 usr +  0.00 sys = 27.56 CPU) @ 1814.03/s
     Hash: 11 wallclock secs (11.62 usr +  0.00 sys = 11.62 CPU) @ 4301.08/s
  HashRef: 12 wallclock secs (12.02 usr +  0.00 sys = 12.02 CPU) @ 4161.12/s