my @data = ("aaaaa") x 10;
my $line = join "\t" => @data;
my $data = join "\n" => map { $line } 0 .. 500000;

=>
         Rate csv_xs  split
csv_xs 1.17/s     --   -13%
split  1.34/s    14%     --
-------------------------------------------------
my @data = ("aaaaa") x 500;
my $line = join "\t" => @data;
my $data = join "\n" => map { $line } 0 .. 50000;

=>
       s/iter  split csv_xs
split    2.93     --   -57%
csv_xs   1.25   134%     --
-------------------------------------------------
my @data = ("aaaaaaaaaaaaaaaaaaaaaaaaaaa") x 500;
my $line = join "\t" => @data;
my $data = join "\n" => map { $line } 0 .. 50000;

=>
       s/iter csv_xs  split
csv_xs   3.74     --    -5%
split    3.55     5%     --