$a{a}{a}{a}

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is short for 
$a{a}->{a}->{a}

[download]

When the operand of a dereference (e.g. LHS of "->") is undef, it gets vivified into the right kind of reference. That means the above is short for 

( ( $a{a} //= {} )->{a} //= {} )->{a}

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Solution? "no autovivification;"

In reply to Re: Why does perl expression in empty nested hash create parents by ikegami
in thread Why does perl expression in empty nested hash create parents by Steve_BZ

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