#!/usr/bin/env perl -l

use strict;
use warnings;

use Time::Piece;
use Time::Seconds;

my %day2t = qw{Fri 0  Sat 1  Sun 2  Mon 3 Tue 4  Wed 5  Thu 6};

my $test_date = '1-Dec-2013';
my $t_now = Time::Piece->strptime($test_date, '%d-%b-%Y');
my $t_mod = $t_now - ONE_DAY * $day2t{$t_now->day};

print 'Time now:      ', $t_now->strftime;
print 'Time modified: ', $t_mod->strftime;