Just for clarification (for the original poster), your syntax:

$hashref{name} = { data1 => "moredata" };
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*replaces* the reference in $hashref{name} with a new one, composed of your data1 => "moredata" hash. That's why it won't work. merlyn is correct in that if you wish to modify the hash referenced by $hashref{name} you don't do that by setting $hashref{name}, you modify it as if it were a hash: $hashref{key}{subkey} = $xyz;