Benchmark: timing 1000000 iterations of eq, index, regex, regex_anch...
        eq:  1 wallclock secs ( 0.88 usr +  0.00 sys =  0.88 CPU) @ 1136363.64/s (n=1000000)
     index:  0 wallclock secs ( 1.65 usr +  0.00 sys =  1.65 CPU) @ 606060.61/s (n=1000000)
     regex:  0 wallclock secs ( 1.08 usr +  0.00 sys =  1.08 CPU) @ 925925.93/s (n=1000000)
regex_anch:  2 wallclock secs ( 1.59 usr +  0.00 sys =  1.59 CPU) @ 628930.82/s (n=1000000)
                Rate      index regex_anch      regex         eq
index       606061/s         --        -4%       -35%       -47%
regex_anch  628931/s         4%         --       -32%       -45%
regex       925926/s        53%        47%         --       -19%
eq         1136364/s        87%        81%        23%         --