Benchmark: timing 10000000 iterations of index, regex, shortindex, shortregex, substrindex, substrregex...
     index: 18 wallclock secs (17.29 usr +  0.00 sys = 17.29 CPU) @ 578369.00/s (n=10000000)
     regex: 32 wallclock secs (32.52 usr +  0.00 sys = 32.52 CPU) @ 307503.08/s (n=10000000)
shortindex: 15 wallclock secs (15.15 usr +  0.00 sys = 15.15 CPU) @ 660066.01/s (n=10000000)
shortregex: 26 wallclock secs (27.14 usr +  0.00 sys = 27.14 CPU) @ 368459.84/s (n=10000000)
substrindex:  9 wallclock secs ( 9.39 usr +  0.00 sys =  9.39 CPU) @ 1064962.73/s (n=10000000)
substrregex: 17 wallclock secs (16.64 usr +  0.00 sys = 16.64 CPU) @ 600961.54/s (n=10000000)
                 Rate  regex shortregex index substrregex shortindex substrindex
regex        307503/s     --       -17%  -47%        -49%       -53%        -71%
shortregex   368460/s    20%         --  -36%        -39%       -44%        -65%
index        578369/s    88%        57%    --         -4%       -12%        -46%
substrregex  600962/s    95%        63%    4%          --        -9%        -44%
shortindex   660066/s   115%        79%   14%         10%         --        -38%
substrindex 1064963/s   246%       189%   84%         77%        61%          --