You're right that the first of your suggested forms is the recommended method for maximum comparability.
Incidentally, any of those 3 forms work counting mine, at least in reasonably-recent Perl versions (though I'm not exactly sure how old would break with that.) I had intended for the form that dropped the leading v as the documentation says it's more backwards-compatible, but there it is.
In reply to Re^3: When was $@ scope in sigdie fixed?
by Apero
in thread When was $@ scope in sigdie fixed?
by Boldra
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