Just a quick review: you are overwriting because of: %{$href} = %{JSON::PP->new->decode($json_data)};

Ie: as you noted, at each file iteration you are reassigning the content of $haref with new data.

You must instead do something like:

# untested
foreach my $key ( keys %{JSON::PP->new->decode($json_data)}  ){

 # some collision check?
 if ( exists $$href{ $key }){
    warn "$key already exists! was [$$href{ $key }] and will be [${JSO
+N::PP->new->decode($json_data)}{$key}]\n";
 }

 # assign a new key value pair
 
 $$href{$key} = ${JSON::PP->new->decode($json_data)}{$key};


}
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Try, before dealing with your JSONS, with a bounch of test hashes until you get it working.

Also I'd avoid subs named encode and decode because of the risk of collision and for readability: if I see encode when using a JSON module I think about the module method ;)

HtH

L*