So *%data = *%values should be compiled as ...

But this would implicitly cast the plain assignment to a binding, which is kind of icky, hence the reason I suspect that %data will be clobbered.

So the question here is, is $fish eq "hest" after this, or undef?

I think in the first example $fish will become undef as part doesn't return enough args. Not only that, because of the lack of binding, the LHS will be assigned whatever part returns in the order it is returned. As for the second example, you still have the problem of lack of binding, and you're assigning a pair to nothing, and if the value of a pair is assigned to when a pair is used on the LHS of a simple assign then you might get a compile-time error as you'd be assigning to the constant string "hest".

Update (WRT to Cine's update): given your definition of := then nothing would happen to $fish as it would have nothing to bind to, and I'm hoping that would be how it is implemented, as binding a variable to nothing doesn't make much sense.
HTH

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