Benchmark: timing 10000000 iterations of comp, exist, regex...
      comp: 56 wallclock secs (55.39 usr +  0.00 sys = 55.39 CPU)
     exist: 50 wallclock secs (49.34 usr +  0.00 sys = 49.34 CPU)
     regex: 79 wallclock secs (79.32 usr +  0.00 sys = 79.32 CPU)