Object as hash key

Is it possible to use an object as a hash key?

For example, the following code allows me to use an instance of MyClass as a key but when I iterate over the keys and attempt to invoke the get_value method, I get the error:

Can't locate object method "get_value" via package "MyClass=HASH(0x12a4040)" (perhaps you forgot to load "MyClass=HASH(0x12a4040)"?)

package MyClass;
use strict;

sub new
{
    my $class = shift;
    my $self = {
        _value => shift
    };
    bless $self, $class;
    return $self;
}

sub get_value {
    my($self) = @_;
    return $self->{_value};
}

my %hash = ();
%hash->{new MyClass(1)} = 0;
%hash->{new MyClass(2)} = 1;

for my $key (keys %hash)
{
    print $key->get_value;
}