Because it's not an operator of itself. It's an assignment to a list further piped into another assignment. It's just a means to create a list context. Others may find a better wording to describe it: possibly mine is not as technically accurate as it could be. Unfortunately as others already explained, it's not reliable to use it with split.

In reply to Re^3: Counting the number of items returned by split without using a named array by blazar
in thread Counting the number of items returned by split without using a named array by Anonymous Monk

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