I reading programming perl, at chapter 12, the objects, has following documents :

The next::method has a similar problems because it uses the package of its
caller to figure out what class to look at. If you define a method in Donkey from
another package, next::method will break:

package main;
*Donkey::sound = sub { (shift)–>next::method(@_) };
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The anonymous subroutine shows up in the stack with as _ _ANON_ _, so next::method doesn’t know which package it is in. You can use the Sub::Name CPAN module to make it work out, though:

use Sub::Name qw(subname);
*Donkey::sound =
subname 'Donkey::sound' => sub { (shift)–>next::method(@_) };
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I am very inquisitive how Sub::Name module complete this work ? let the anonymous subroutine's caller not be __ANON__

very thanks your help :)