It aliases $item to $items{ $row->{item_key} }. Changes to one affect both. I could have done $item_ref = \( $items{ $row->{item_key} } );, but it made the subsequent code rather messy (but not as much as using neither).

In reply to Re^3: Grouping an array of hashrefs by similar key values by ikegami
in thread Grouping an array of hashrefs by similar key values by perldj

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