As described in perlop, ~ is the bitwise negation operator. A substitution returns the number of substitutions performed, though I can't imagine a good reason why you'd want bitwise negation of that return value.

Update: After reading JavaFan's comment below, I think you're looking at a victim of refactoring where no bugs were introduced.

In reply to Re: Operator/Regex question by kennethk
in thread Operator/Regex question by Migloth

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