It works like this :

#!/usr/bin/perl 

use strict;
use warnings;

use Benchmark qw[cmpthese timethese];

my @A = qw[this that these those];
my $result;

open my $null, '>', '/dev/null' or die;

$result = timethese(
    -5, 
    {   
        test      => sub { print {$null} "@A" },
        with_for  => sub { print {$null} $_ for @A },
        with_join => sub { print {$null} join '', @A },
    }
);

cmpthese( $result, 'none' );
[download]

OUTPUT :
Benchmark: running test, with_for, with_join for at least 2 CPU second
+s...
      test:  3 wallclock secs ( 2.03 usr +  0.01 sys =  2.04 CPU) @ 64
+2509.31/s (n=1310719)
  with_for:  1 wallclock secs ( 2.14 usr +  0.00 sys =  2.14 CPU) @ 49
+4696.26/s (n=1058650)
 with_join:  2 wallclock secs ( 2.16 usr +  0.00 sys =  2.16 CPU) @ 93
+5679.63/s (n=2021068)
[download]

HTH,
PooLpi