An alternative:

use Data::Heap::Whatever 1.1 ( Factory => my $Heap, ...
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But the passing of a reference has two purposes:

1. It lets us reliably distinguish between an option name and a variable being passed in to receive a factory, thus allowing the more stream-lined usage
2. It makes the fact that $Heap will be modified explicit, serving as a form of documentation

I don't have a strong preference (other than wishing use could return a factory), though.