Another way to get yesterday's date:

#!/usr/bin/perl

use warnings;
use strict;

use Time::Local 'timelocal_nocheck';

sub days_before_now {
    my @date = localtime;
    return timelocal_nocheck(@date[0..2],$date[3]-$_[0], @date[4,5]);
}

print scalar( localtime days_before_now(1)), "\n";
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days_before_now(-1) will return the tomorrow's date ;)