If you check the prototype, pop is ";+"

No, not anymore, this was an experiment added in Perl 5.14 and removed in 5.24; see "Array and hash container functions accept references" (aka "autoderef") in perlexperiment. Its prototype has gone back to ;\@, like it was in 5.12 and below. The removal of the feature is why the "Experimental pop on scalar is now forbidden" error happens in the first place.

In reply to Re^2: passing an array without a name to pop() by haukex
in thread passing an array without a name to pop() by TieUpYourCamel

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