You *can* do that, but then end up copying a bunch of memory around, whereas when you use a reference you're just copying, well, the reference. So personally I think it's generally better to just use references as arguments. It's faster.

In addition, what if you later decided that you needed to call the subroutine with two hash arguments instead of just one? Now you've got a problem, because you can't say:

    foo(%bar, %baz);
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because the hashes get flattened into a list (as all subroutine arguments do). So instead you've got to pass in references to the hashes, and now you'll have to change all mentions of the hash inside the subroutine to use the reference instead.

So it'll save you possible future work to use references.