use strict;
use warnings;

use Benchmark q{cmpthese};

my $nullFile = q{/dev/null};
open my $nullFH, q{>}, $nullFile
   or die qq{open: $nullFile: $!\n};

my $rcConcat = sub
   {
       print $nullFH q{a} . q{!} x 5 for 1 .. 10000;
   };

my $rcList = sub
   {
       print $nullFH q{a}, q{!} x 5 for 1 .. 10000;
   };

cmpthese (-3,
   {
      Concat     => $rcConcat,
      List       => $rcList,
   });

close $nullFH
   or die qq{close: $nullFile: $!\n};

##</code><code>##

$ for i in 1 2 3 4 5 6 7 8 9 10; do
> echo Run $i
> ./spw613222
> done
Run 1
         Rate Concat   List
Concat 17.4/s     --    -9%
List   19.2/s    10%     --
Run 2
         Rate Concat   List
Concat 17.4/s     --   -10%
List   19.3/s    11%     --
Run 3
         Rate Concat   List
Concat 17.5/s     --   -10%
List   19.4/s    11%     --
Run 4
         Rate Concat   List
Concat 17.5/s     --    -9%
List   19.1/s     9%     --
Run 5
         Rate Concat   List
Concat 17.4/s     --   -10%
List   19.3/s    11%     --
Run 6
         Rate Concat   List
Concat 17.4/s     --   -10%
List   19.4/s    11%     --
Run 7
         Rate Concat   List
Concat 17.5/s     --   -10%
List   19.4/s    11%     --
Run 8
         Rate Concat   List
Concat 17.5/s     --   -10%
List   19.4/s    11%     --
Run 9
         Rate Concat   List
Concat 17.5/s     --   -10%
List   19.4/s    11%     --
Run 10
         Rate Concat   List
Concat 17.4/s     --   -10%
List   19.3/s    11%     --
$