Benchmark: timing 1000000 iterations of compl, exist, regex, tr...
     compl: 17 wallclock secs (17.35 usr +  0.02 sys = 17.37 CPU)
     exist: 15 wallclock secs (14.02 usr +  0.01 sys = 14.03 CPU)
     regex: 18 wallclock secs (18.62 usr +  0.00 sys = 18.62 CPU)
        tr: 16 wallclock secs (16.67 usr +  0.01 sys = 16.68 CPU)