In your case, it's not $$_, but $$_[...]. The $$... is dereferencing a reference.

$$_[...] can be rewritten as $_->[ ... ], which might make the indexing of an array more obvious to you. See also References Quick Reference.

In reply to Re: Code clarification - use of map and $$_ by Corion
in thread Code clarification - use of map and $$_ by Anonymous Monk

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