Thank you very much for your vivid elaboration which is very inspiring. =D
Why are you doing that?
Because when an object fall into a thread scope, the object will be cloned, which is not the one I want. And since threads don't share object / complex data structure ( and I don't what to share them one by one ), this trick do share the object perfectly... until it's not.

Actually, I can do the job with simply: @dirToFetch : shared, but same issue Thread::Queue, I gotta leave it at a nested package scope , but create it inside an object become another mess to share around threads. Because I attempt to make it a module, so I hope to avoid if other script calling this module in threads, the data will mess up.

Though, I've update my OP's code, which will work and as fast as dir /s/b I create as many threads as how much in @dirToFetch

In reply to Re^2: use threads for dir tree walking really hurts by exilepanda
in thread use threads for dir tree walking really hurts by exilepanda

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