In the OP's code. The return $a lines will return values like 'etc'. Sort expects -1, 0 or 1 as is returned by cmp and <=>.

Premature optimization is the root of all job security

In reply to Re^3: Argument isn't numeric in sort -- resolve or ignore? by GrandFather
in thread Argument isn't numeric in sort -- resolve or ignore? by Argel

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