G'day thirtySeven,

Welcome to the Monastery.

I see you've indicated that ++hippo's solution is what you want.

You did say "without mutating any variables"; however, that solution will require mutating variables, e.g.:

$mon += 1;
$yr += 1900;
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See localtime for an explanation of that.

My local time:

$ date
Thu,  7 Jan 2021 09:03:14
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Values from localtime:

$ perl -E 'say for (localtime)[1..5]'
3
9
7
0
121
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There is a built-in module, Time::Piece, that will handle those extra calculations for you. See the documentation for a variety of ways to use that module. For a direct comparison with the output from localtime above:

$ perl -E 'use Time::Piece; my $t = localtime; say $t->$_ for qw{min h
+our mday mon year}'
3
9
7
1
2021
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Note that Time::Piece was released with Perl 5.10.0 — see "perl5100delta: New modules" — so you'll need that version or later to use this. If you are working with an older version, I'd recommend updating: the latest stable version is 5.32.0.