Benchmark: timing 1000000 iterations of index, s///, substr...
     index: 15 wallclock secs (14.02 usr +  0.00 sys = 14.02 CPU) @ 71326.68/s (n=1000000)
      s///: 13 wallclock secs (12.33 usr +  0.00 sys = 12.33 CPU) @ 81103.00/s (n=1000000)
    substr: 14 wallclock secs (13.37 usr +  0.00 sys = 13.37 CPU) @ 74794.32/s (n=1000000)
          Rate  index substr   s///
index  71327/s     --    -5%   -12%
substr 74794/s     5%     --    -8%
s///   81103/s    14%     8%     --