"@{ $hash{$query} }" means "the array referenced by the reference stored in $hash{$query}". However, $hash{$query} does not contain a reference to an array. It contains the string "query".

If $hash{$query} is undefined and @{ $hash{$query} } is used as an lvalue (like when it's an argument to push), an array will automatically be created and a reference to that array will be stored in $hash{$query}. This is called autovivification.

Get rid of the line $hash{'query'}= $query; (to allow autovivification).

In reply to Re: Can't use string ("query") as an ARRAY ref error by ikegami
in thread Can't use string ("query") as an ARRAY ref error by Anonymous Monk

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