Date::Calc is really useful for this sort of item.

use strict;
use Date::Calc qw(Add_Delta_Days);

my (undef, undef, undef, $day, $month,$year)  = localtime();
$year+=1900;
$month+=1;

($year,$month,$day) = Add_Delta_Days($year,$month,$day, -3);
print join("-", $year,$month,$day)
[download]

Using localtime() is a little bit easier (and more portable, if that matters) than calling date from the shell. Good luck.

    --jaybonci