If I have a reference $ref to a data structure or a blessed reference, then if I print "$ref" I get strings like "HASH(0x17653d4)" or "Module=HASH(0x17653d4)". I don't know what this means or what use it is intended for. Are these strings unique? Can I maybe use them as keys in a hash to store object individual and private information? I have tried this in the following code. It even happend to work but I wouldn't dare to use it whithout knowing what these strings really are. If you know a place that explains the meaning of stringified references, please post it. 
$o = new Module;
$o->method;

package Module;
{
    my %obj;
    sub new {
        my $class = shift;
        my $self = {@_};
        bless $self, ref($class) || $class;
        $obj{"$self"} = { say => "Hello World"};
        $self;
    }
    sub method {
        my $self = shift;
        my $obj = $obj{"$self"};
        return $obj->{say};
    }
    DESTROY {
        my $self = shift;
        delete $obj{"$self"};
    }
}

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In reply to What is HASH(0x17653d4) for? by Tetramin

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