I might be missing the point but why are you poking around the internals of the object?

The docs for Net::Amazon::Response shows that properties() returns an array of objects (each of which is a Net::Amazon::Property::* object I guess)

if($resp->is_success) { 
    foreach my $property ($resp->properties) {
        # $property isa Net::Amazon::Property object
        # print $property->as_string, $/;
        print $property->ProductName, ' ',
              $property->ReleaseDate, $/;   
    }
}
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