I find your example rather misleading as your variable $HASH is not referring to a hash structure at all but to an array. You are using push, which pushes an element onto the right-hand, or top, end of an array and you are using the @ sigil to dereference $HASH to get at the array it refers to. You say "dump the whole hash" when using Data::Dumper but again you are supplying a reference to an array and, by enclosing the argument in anonymous hash constructors Data::Dumper->Dump([$HASH]), you are actually going to see an array of arrays in your output. Something like

$VAR1 = [
           [
              'data1',
              'data2',
              'data3'
           ]
        ];
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Later you loop over the array printing out each element but you confuse things again by referring to each as a key. Arrays don't have keys, hashes do. Also, why do you declare the scalar $value then never use it?

Cheers,

JohnGG