Perl version: v5.12.0
Length of string: 140000
           Rate  [Aa]{2}       lc [Aa][Aa]       /i
[Aa]{2}  50.7/s       --      -0%      -1%      -3%
lc       50.8/s       0%       --      -1%      -3%
[Aa][Aa] 51.5/s       1%       1%       --      -2%
/i       52.5/s       4%       3%       2%       --