use Date::Simple ('date', 'today');
my $date = today();
print "Today is: "     , $date, "\n";
print "Tomorrow is: "  , $date + 1, "\n";
print "Yesterday is: " , $date - 1, "\n";
[download]

Update: oops... didn't see your updated code

$today_tmp = DateTime->now();
$tomorrow_tmp = DateTime->now()->add( days => 1 );
$yesterday_tmp = DateTime->now()->subtract( days => 1 );
$today = $today_tmp->mdy('/');
$tomorrow = $tomorrow_tmp->mdy('/');
$yesterday = $yesterday_tmp->mdy('/');
print "Today: $today -=- ";
print "Tomorrow: $tomorrow -=- ";
print "Yesterday: $yesterday -=- ";
[download]

Works perfectly!

No, it doesn't. I thought you wanted the local date, not the date halfway around the world. If so, you introduced a bug by removing time_zone => 'local'. (Yeah, I had it misspelled.)

I'm also curious as to why you changed from today to now.

I actually do want the date half way around the world :) The 'local' was taken out because the script is still a work-in-progress, so to speak.

I've got the following now:

...
my $tz_ny = "America/New_York";
my $tz_ln = "Europe/London";
my $tz_tk = "Asia/Tokyo";
my $tz_hk = "Asia/Hong_Kong";
my $tz_se = "Asia/Seoul";
my $tz_mo = "Europe/Moscow";
...
if ($region =~ /ny/) {
        $today_tmp = DateTime->now( time_zone => $tz_ny);
        print "it is $today_tmp now in NY\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
} elsif ($region =~ /ln/) {
        $today_tmp = DateTime->now( time_zone => $tz_ln);
        print "it is $today_tmp now in LN\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
} elsif ($region =~ /tk/) {
        $today_tmp = DateTime->now( time_zone => $tz_tk);
        print "it is $today_tmp now in TK\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
} elsif ($region =~ /hk/) {
        $today_tmp = DateTime->now( time_zone => $tz_hk);
        print "it is $today_tmp now in HK\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
} elsif ($region =~ /se/) {
        $today_tmp = DateTime->now( time_zone => $tz_se);
        print "it is $today_tmp now in SE\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
} elsif ($region =~ /mo/) {
        $today_tmp = DateTime->now( time_zone => $tz_mo);
        print "it is $today_tmp now in MO\n";
        $tomorrow_tmp = DateTime->now()->add( days => 1 );
        $yesterday_tmp = DateTime->now()->subtract( days => 1 );
}

$today = $today_tmp->mdy('/');
$tomorrow = $tomorrow_tmp->mdy('/');
$yesterday = $yesterday_tmp->mdy('/');
print "Today ($region): $today -=- ";
print "Tomorrow ($region): $tomorrow -=- ";
print "Yesterday ($region): $yesterday -=- ";
$next_business_day = `$holiday_script "$today" $region`;
chomp($next_business_day);
print "Next business day: $next_business_day\n";
$today_local_tmp = DateTime->now( time_zone => 'local');
$tomorrow_local_tmp = DateTime->now()->add( days => 1 );
$yesterday_local_tmp = DateTime->now()->subtract( days => 1 );
$today_local = $today_local_tmp->mdy('/');
$tomorrow_local = $tomorrow_local_tmp->mdy('/');
$yesterday_local = $yesterday_local_tmp->mdy('/');
print "Today (local (NY) ): $today_local -=- ";
print "Tomorrow (local (NY) ): $tomorrow_local -=- ";
print "Yesterday (local (NY) ): $yesterday_local -=- ";
$next_business_day_local = `$holiday_script "$today" ny`;
chomp($next_business_day_local);
print "Next business day (local (NY) ): $next_business_day_local\n";
...
[download]

So in essence I have 2 variables - one for whatever timezone I'm interested in at the moment, and another one that always contains local time.

As for now and today - was just playing around and replaced it, then never switched it back :)