This is because of autovivification, which is described in Using References. When you dereference your array element as if it were a reference to a hash, an anonymous hash is created and the array element is set to a reference to that hash. If your array element were not undefined, this would not happen - it would be a hash reference or not and so it would work or you would get an error.

In reply to Re: Why nothing from 'strict' or 'warnings' with deref'd undef value? by ig
in thread Why nothing from 'strict' or 'warnings' with deref'd undef value? by jeremym

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