$ perl -MO=Deparse -e '{use strict; my $a = 1}'
{
    use strict 'refs';
    my $a = 1;
}

##</code><code>##

use Benchmark qw(:all);
cmpthese( 10000000, {
   with => sub {use strict 'refs'; my $a = 1; my $b = 2},
   without => sub {my $a = 1; my $b = 2},
} );
__END__
             Rate    with without
with    3378378/s      --     -7%
without 3623188/s      7%      --

             Rate without    with
without 3802281/s      --     -3%
with    3937008/s      4%      --

             Rate    with without
with    3412969/s      --    -15%
without 4032258/s     18%      --

             Rate    with without
with    4048583/s      --     -3%
without 4166667/s      3%      --

             Rate    with without
with    3460208/s      --     -9%
without 3787879/s      9%      --