use warnings;

my %hash1 = (
	bush => "A",
	tree => "A"
);

my %hash2 = (
	dog => "A",
	cat => "A"
);

my %hash3 = (
	plants    => \%hash1,
	animals   => \%hash2
);

my %hash4 = (
	plants    => \%hash1,
	animals   => \%hash2
);

print "$hash3{plants}{bush}\n";
print "$hash4{plants}{bush}\n";
print "\n";
$hash4{plants}{bush}="B";
print "$hash3{plants}{bush}\n";
print "$hash4{plants}{bush}\n";