Benchmark: timing 100000 iterations of NoOpLoop, regex1, reverse, substr...
  NoOpLoop:  2 wallclock secs ( 1.86 usr +  0.00 sys =  1.86 CPU) 
             @ 53763.44/s (n=100000)
    regex1: 82 wallclock secs (30.31 usr +  0.01 sys = 30.32 CPU) 
             @ 3298.15/s (n=100000)
   reverse:  8 wallclock secs ( 7.40 usr +  0.00 sys =  7.40 CPU) 
             @ 13513.51/s (n=100000)
    substr:  8 wallclock secs ( 8.51 usr +  0.01 sys =  8.52 CPU) 
             @ 11737.09/s (n=100000)