Benchmark: timing 1000000 iterations of Closure, Global, Lexical, Recursion...
   Closure: 66 wallclock secs (61.70 usr +  0.00 sys = 61.70 CPU) @ 16207.46/s (n=1000000)
    Global: 62 wallclock secs (58.39 usr +  0.00 sys = 58.39 CPU) @ 17126.22/s (n=1000000)
   Lexical: 63 wallclock secs (58.55 usr +  0.00 sys = 58.55 CPU) @ 17079.42/s (n=1000000)
 Recursion: 208 wallclock secs (176.95 usr +  0.00 sys = 176.95 CPU) @ 5651.31/s (n=1000000)