Run against 24 character string:
          Rate  regex unpack substr
regex  40260/s     --   -17%   -44%
unpack 48660/s    21%     --   -33%
substr 72138/s    79%    48%     --


Run against 480000 character string:
          Rate  regex unpack substr
regex  0.983/s     --   -10%   -60%
unpack  1.10/s    11%     --   -55%
substr  2.44/s   148%   122%     --