my $hash;
$hash{foo} = bar;

##</code><code>##

my %hash;
$hash{foo} = 'bar';

#Versus

my $hash = {};
$hash->{foo} = 'bar';

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

print "A lexical hash:\n";
my %hash;
$hash{foo} = 'bar';
print Dumper(\%hash);

print "A lexical hash *reference*:\n";
my $hash = {};
$hash->{foo} = 'bar';
print Dumper(\$hash);