The problem is that you are confusing a reference to an array with the array itself. Your $data variable is a scalar (not an array) whose value is a reference to an array. You need to use indirection to get at the elements of the array. These are all equivalent:

    $$data[0]
    ${$data}[0]
    $data->[0]
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Personally, I prefer the third form but if you're trying to create obfuscated code use the first form.