X:\>perl -w tmp.pl
Running with a dataset of 200000000
                       Rate tr_via_readline 10k tr_via_readline 100k tr_via_readline 1m tr_map_file tr_in_memory
tr_via_readline 10k  2.18/s                  --                 -15%               -17%        -71%         -76%
tr_via_readline 100k 2.55/s                 17%                   --                -2%        -66%         -72%
tr_via_readline 1m   2.61/s                 20%                   2%                 --        -66%         -72%
tr_map_file          7.60/s                249%                 198%               191%          --         -18%
tr_in_memory         9.25/s                325%                 263%               254%         22%           --