For definitive information about US Copyrights, go here: http://www.copyright.gov.   There’s no need to speculate.

The notice-requirements require the symbol and/or the word, the claimant’s name or fictitious name, and the year.

A copyright will persist for quite a few years after your death.   (Ahem...)   Each time I make a major change to a copyrighted work, and file a new registration form, I update the year on my notices, which include both the first and the most-recent date of registration.   Someone searching the LOC database on either year would find my certificate.   But I am talking about a commercial product that (still) provides quite a bit of my daily bread, and against which I have indeed had to file some “cease and desist” letters, one of which was briefly (and of course, unsuccessfully) challenged.   In that context, attention to detail was important.   But for your Perl module, I would suggest that “the choice, oh Registered Copyright-Owner, is mostly yours.”