You ignore that join also has a prototype. When you write 
join @_;

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Then the @_ is evaluated in scalar context as the separator, with an empty list of items to join.

So join and myjoin evaluate their arguments differently, and it's no surprise that they lead to difference in autovivification.

Perl 6 - second systems done right

In reply to Re: Autovivification and hash slices by moritz
in thread Autovivification and hash slices by norbert.csongradi

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