Saying it this way

use Juliet 1.1;
our @ISA = 'Juliet';
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actually makes the most sense to me -- but I'm uneasy about twiddling with @ISA since that's how Perl gets told about inheritance.

Hiding @ISA with your middle example

use Juliet 1.1;
use parent 'Juliet';
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is less alarming -- but it seems like it does the same thing.