Its probably to late, but I do want to point out that your original code would work as intended (and perhaps even be clearer) if you test the levels separately. The "short circuit" feature of the "and" operator prevents the troublesome low-level test from running unless the upper-level key exists.

    if (    exists $auto_picks{ $data[0] }
        and exists $auto_picks{ $data[0] }{ $data[1] } )
    {
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