use strict;
use warnings;

use Benchmark qw( cmpthese );

my $passes = 100_000;
my $tests  = -10;

sub with {
   use warnings;
   my $i = 0;
   $i = $i + 1         # Undefined check
      for 0..$passes;
   1;
}

sub without {
   no warnings;
   my $i = 0;
   $i = $i + 1         # No undefined check
      for 0..$passes;
   1;
}

cmpthese($tests, {
   with    => \&with,
   without => \&without,
});

##</code><code>##

Benchmark: running with, without, each for at least 10 CPU seconds...
      with: 10 wallclock secs (10.24 usr +  0.00 sys = 10.24 CPU) @ 20.40/s (n=209)
   without: 11 wallclock secs (10.40 usr +  0.01 sys = 10.41 CPU) @ 20.47/s (n=213)
          Rate    with without
with    20.4/s      --     -0%
without 20.5/s      0%      --