$ perl bench_split.pl
            s/iter filehandle3       regex       index       split  filehandle
filehandle3   3.64          --         -7%        -16%        -39%        -51%
regex         3.38          8%          --         -9%        -34%        -47%
index         3.07         18%         10%          --        -28%        -42%
split         2.22         64%         52%         38%          --        -20%
filehandle    1.77        105%         90%         73%         25%          --