Going way back to code from (tye)Re: varying length multi-dimensional hashes, I'd use:

    my $ref= \\%pkg;
    for my $key (  split /::/, $pkg  ) {
        $ref= \$$ref->{$key};
    }
    $$ref= $pkg;
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in the middle of your code.

        - tye (I keep that filed away under "real use for \\")