cmpthese(0, {
              substr => sub {
                  my @l = @list;
                  substr $_, -2, 0, '.' for @l;
              },
              regex => sub {
                  my @l = @list;
                  s/(..)$/.$1/ for @l;
              },
              regex2 => sub {
                  my @l = @list;
                  s/(?=..)$/./ for @l;
              },
             });
##</code><code>##

         Rate substr  regex regex2
substr 73.1/s     --   -39%   -71%
regex   121/s    65%     --   -52%
regex2  250/s   242%   107%     --