It you want to sort anything in Perl fast, then go for Sort::Key!!!

use Sort::Key::Multi qw(ii_keysort);

...
my %methods = (
   ...
   skm => sub
   {
       my @sorted = ii_keysort { (split m{,}, $_, 3 )[ 1, 0 ] } @{$_[0
+]};
       return \@sorted
   }
   );
[download]

That's what I get on my computer:

             Rate nSubSplit nSubRegex nSubSplit3 stSplit stSplit3 stRe
+gex grtSplit grtRegex grtSplit3  skm
nSubSplit  21.7/s        --      -54%       -61%    -75%     -83%    -
+84%     -85%     -91%      -91% -95%
nSubRegex  47.6/s      119%        --       -14%    -46%     -63%    -
+65%     -67%     -80%      -81% -89%
nSubSplit3 55.6/s      156%       17%         --    -36%     -56%    -
+60%     -62%     -77%      -77% -87%
stSplit    87.5/s      303%       84%        57%      --     -31%    -
+36%     -40%     -64%      -64% -80%
stSplit3    127/s      486%      167%       129%     45%       --     
+-8%     -12%     -48%      -48% -70%
stRegex     138/s      534%      189%       147%     57%       8%     
+ --      -5%     -43%      -44% -68%
grtSplit    145/s      569%      205%       161%     66%      14%     
+ 6%       --     -40%      -41% -66%
grtRegex    243/s     1021%      411%       338%    178%      91%     
+77%      68%       --       -1% -43%
grtSplit3   245/s     1029%      415%       341%    180%      93%     
+78%      69%       1%        -- -43%
skm         431/s     1885%      805%       674%    393%     239%    2
+13%     197%      77%       76%   --
[download]