The core modules Time::Piece and Time::Seconds make this very easy.

#!/usr/bin/env perl
use strict;
use warnings;

use Time::Piece;
use Time::Seconds;

my $now = localtime;
print "Today is $now\n";
my $tp = $now - ONE_DAY;
print "Yesterday was $tp\n";
$tp = $now + ONE_DAY;
print "Tomorrow will be $tp\n";
$tp = $now - 7 * ONE_DAY;
print "A week ago was $tp\n";
$tp = $now + 7 * ONE_DAY;
print "Next week will be $tp\n";
$tp = $now->add_months (-1);
print "A month ago was $tp\n";
$tp = $now->add_months (1);
print "Next month will be $tp\n";
$tp = $now->add_years (-1);
print "A year ago was $tp\n";
$tp = $now->add_years (1);
print "Next year will be $tp\n";
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