in reply to how to get the parent class method of the parent class itself

Several problems:
  1. The code misses indentation. It made it hard for me to help you.
  2. display is not dislpay. Please, post the code that actually runs and shows the problem.
  3. Have you read mro? You are using get_linear_isa differently from its documentation: 
    my $gp = mro::get_linear_isa(ref $obj)->[1];

    [download]

    This puts a string to $gp, so you can't dereference it as an array later.

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