...
use Sort::Key qw(keysort);
...
cmpthese(-3, {
    ...
    sk => '
        use strict; use warnings;
        my @sorted = keysort { substr($_, -(19+20), 19) } @::LogFileList;
    ',
});

##</code><code>##

            Rate memoized       st      grt    naive       sk
memoized  8784/s       --     -26%     -51%     -54%     -58%
st       11894/s      35%       --     -33%     -38%     -43%
grt      17794/s     103%      50%       --      -7%     -14%
naive    19207/s     119%      61%       8%       --      -7%
sk       20714/s     136%      74%      16%       8%       --