Rate reference   regular
reference 8.00/s        --       -8%
regular   8.73/s        9%        --
                Rate   regularPass referencePass
regularPass   7.19/s            --          -33%
referencePass 10.7/s           49%            --

##</code><code>##

use strict;
use warnings;
use Benchmark qw(cmpthese);

my %hash;
my $hash;

cmpthese (30, {"regular" => \&regular, "reference" => \&reference});
cmpthese (30, {"regularPass" => \&regularPass, "referencePass" => \&referencePass});

sub regular {
    our %hash;
    for my $i (1 .. 100000) {
        $hash{$i} = $i;
    }
}

sub reference {
    our $hash;
    for my $i (1 .. 100000) {
        $hash->{$i} = $i;
    }
}

sub regularPass {
    our %hash;
    for my $i (1 .. 100000) {
      helper(\%hash);
    }
}

sub referencePass {
    my $hash;
    for my $i (1 .. 100000) {
      helper($hash);
    }
}

sub helper {
    my $hash = shift;
}