You're already using
Date::Calc, so I'd go with Add_Delta_Days:
#!/usr/bin/perl -w
use strict;
use warnings;
use Date::Calc qw{ :all };
my ($year, $mon, $day) = Today();
show_date("Today's date", $year, $mon, $day);
($year, $mon, $day) = Add_Delta_Days($year, $mon, $day, -30);
show_date("30 days ago", $year, $mon, $day);
sub show_date {
my ($label, $year, $mon, $day) = @_;
my $date = sprintf "%04d-%02d-%02d", $year, $mon, $day;
print "$label: $date\n";
}
__END__
[Output]
Today's date: 2013-06-07
30 days ago: 2013-05-08
Update: Oh, now I see why you're getting different answers. It's because in:
$date[3] -= 4 * 7;
...
my $month_ago_3 = strftime('%Y-%m-%d', localtime(time - 4 * 7 * 86400
+));
You're subtracting 4 * 7 days (ie. 4 weeks), rather than 30 days.
Does that help?
say
substr+lc crypt(qw $i3 SI$),4,5