use DateTime 0.10;

my $today = DateTime->now();
warn $today->time_zone_short_name();
warn $today->datetime();


$today->subtract( months => 1 );
# or $today->subtract_duration( DateTime::Duration->new( months => 1 ) );

warn $today->datetime();

my $dt = DateTime->last_day_of_month(
    year  => $today->year,
    month => $today->month,
);

die $dt->datetime();
__END__
UTC at soy.pl line 4.
2003-04-28T11:17:32 at soy.pl line 5.
2003-03-28T11:17:32 at soy.pl line 11.
2003-03-31T00:00:00 at soy.pl line 18.