use Data::Dumper;

use strict;

my %a = (1,2,3,4);
my $a_ref = \%a;

print "not ref, without ->\n";
print $a{1}, "\n";#good
print $a{3}, "\n";#good
print "not ref, with ->\n";
print $a->{1}, "\n";#uninitialized
print $a->{3}, "\n";#uninitialized
print "ref, without ->\n";
#print $a_ref{1}, "\n"; #cannot uncomment
#print $a_ref{3}, "\n"; #cannot uncomment
print "ref, with ->\n";
print $a_ref->{1}, "\n";#good
print $a_ref->{3}, "\n";#good