Interesting (I expected a compilation error here, similar as with number predecrement, e.g. --5):

A numeric literal doesn't return an lvalue, but an assignment in scalar context returns an lvalue. See Mini-Tutorial: Scalar vs List Assignment Operator.

In reply to Re: u+ fails to force scalar context to empty list assignment: +( () = ... ) by ikegami
in thread u+ fails to force scalar context to empty list assignment: +( () = ... ) by rsFalse

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