Thank you all so much. So many cool answers and that so quick. I'm impressed.

It took me a while to understand everything. Now I understood it completely and your code is working successfully.

Because my code is also using the _get_attr_data as object and not only as package, I had to rewrite the beginning of _get_attr_data. And I added another cache to this class method, so that not each time the attribute data of a inherited class has to be recomputed again.

...
    # Encapsulated class data

    my %_attr_data; # for each package: stores reference to its attrib
+ute data only
    my %_mro_cache;
    my %_attr_data_cache; # for each package stores reference to its a
+ttribute data + inherited attribute data

    # Class methods to operate on encapsulated class data

    sub _get_attr_data
    {
        my $caller = shift;
        my $package = ref($caller) || $caller;
        return %{$_attr_data_cache{$package}} if defined $_attr_data_c
+ache{$package};      
        my @parents = @{ $_mro_cache{$package} ||= mro::get_linear_isa
+($package) };
        my %return;
        for my $parent (@parents)
        {
            # assure that a reference is inside $_attr_data{$parent}
            ref $_attr_data{$parent} or next;
            for my $attr (keys %{$_attr_data{$parent}})
            {
                $return{$attr} ||= $_attr_data{$parent}{$attr};
            }
        }

        $_attr_data_cache{$package} = {%return};
        
        return %return;
    }
...

[download]

In this case the %_mro_cache should not be needed anymore. Because this method returns if it already handled the attribute data of an inherited package before. Is this method rewritten in a good manner?

Of course you convinced me. I'll learn Moo or Moose and stop using my concept.

Ah, and one other question. In the documentation of ref they write that a direct truth test could be wrong, because 0 which is false could be returned for a reference. Could this happen in my case? When would ref return a 0 for a reference? Would you always recommend to test against the empty string?

In reply to Re^2: Class attribute handling by Dirk80
in thread Class attribute handling by Dirk80

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