my $last_day_month = $t->month_last_day($month); #??

##</code><code>##

$last_day = Time::Piece->new->month_last_day;

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use feature qw/ say /;
use Time::Piece;

for my $year (2015, 2016) {
  say sprintf("$year/%02d: ", $_), Time::Piece->strptime("$year $_", "%Y %m")->month_last_day) for 1,2;
}

__END__


##</code><code>##

$ perl 1140366.pl
2015/01: 31
2015/02: 28
2016/01: 31
2016/02: 29
$