So, is there a module out there that will control the way perl autovivifies

No. If you want to prevent autovivification, you have to code appropriately:

    undef $ref;
    if ("HASH" eq ref $ref && exists $ref -> {"Some key"}) { }
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If you can't assume that $ref is a reference to a hash, you'd need extra testing anyway, even if there wasn't autovivification. For instance:

    $ref = [];
    if (exists $ref -> {key}) { }
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will give you a Can't coerce array into hash error.

Abigail