Scratch that last: 

>perl -E"sub {}->( map $_, @h{x} ); say exists($h{x}) || 0;
1

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map aliases $_ to its operands, so its operands are lvalues. do{} creates copies.

In reply to Re^2: Autovivification and hash slices (rvalue) by ikegami
in thread Autovivification and hash slices by norbert.csongradi

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