To complement, with this I am trying to also get the last day of the last month, here is what I am using, it might be a shorter way as well:

use warnings;
use strict;
use Time::Piece;

my $t = Time::Piece->new();
my $year = $t->year;
my $last_month = $t->add_months(-1)->mon;

# Pass the last month and year to a new Time::Piece object
my $t_last_month  = Time::Piece->strptime("$last_month$year", "%m%Y");

# Now use Time::Piece month_last_day to get it
my $last_day_of_month = $t_last_month->month_last_day;

print "Last Month = $last_month - It's last day = $last_day_of_month \
+n";
[download]

Thanks!