use DateTime;
my $now = DateTime->now;
for ( my $dt = $now->clone->truncate(to=>'month')
		->subtract(years=>2)->add(months=>1);
	  $dt < $now;
	  $dt->add(months=>1) ) {
		my $last = DateTime->last_day_of_month(year=>$dt->year,
			month=>$dt->month,time_zone=>$dt->time_zone);
		print $dt->ymd," to ",$last->ymd,"\n";
}
__END__
2015-07-01 to 2015-07-31
2015-08-01 to 2015-08-31
2015-09-01 to 2015-09-30
...