plain vs reference

gistfile1.pl

#!/usr/bin/env perl
use Modern::Perl;

use Benchmark qw/cmpthese/;

my (@arr1, $arr_ref1, %hash1, $hash_ref1);

say "Read access: ";
my $x;
cmpthese(-2, {
    hash      => sub {
        for my $k (keys %hash1) {
            $x  = $hash1{$k};
        }
    },
    hash_ref  => sub {
        for my $k (keys %hash1) {
            $x = $hash_ref1->{$k};
        }
    },
    array     => sub {
        for my $i (0 .. $#arr1) {
            $x  = $arr1[$i];
        }
    },
    array_ref => sub {
        for my $i (0 .. $#arr1) {
            $x  = $arr_ref1->[$i];
        }
    },
});

say "\n";
say "Write access: ";
cmpthese(-2, {
    hash      => sub {
        for my $i (0 .. 100) {
            $hash1{$i} = $i;
        }
    },
    hash_ref  => sub {
        for my $i (1 .. 100) {
            $hash_ref1->{$i} = $i;
        }
    },
    array     => sub {
        for my $i (1 .. 100) {
            $arr1[$i] = $i;
        }
    },
    array_ref => sub {
        for my $i (1 .. 100) {
            $arr_ref1->[$i] = $i;
        }
    },
});