Reread my sample and use that thing on your shoulders that prevents your hair falling down your throat and forming a hair ball. My sample isn't intended to be a complete answer to your problem. It is intended to show you some tools and an approach using those tools to solve your problem. It is also intended to be self contained so that you can easily reproduce the output I indicated that it generates. It should be pretty obvious how you plug in your own local files in place of the "internal files" used in the sample.

The sample prints out more information that you asked for because that demonstrates how to store information (such as line number) for the data in the hash and how to access that ancillary information.

Because you don't tell us the back story and don't provide context details such as "duplicate keys can/can't exist", the sample code assumes that not only duplicate keys may exist, but that their context is important. You may wish to consult perllol to gain some insight into how the hash of array (hoa) works if you've not encountered it before (or take a trip to the Tutorials section).