#!/usr/bin/perl

use v5.10;
use strict;
use warnings;

use DateTime;

my $dt1 = DateTime->new( year => 2013, month => 7, day => 5 );
my $dt2 = $dt1->clone->add( days => 15 );
if ( $dt2->dow > 5 ) {  # July 20, 2013 happens to be a Saturday
    say "$dt2 falls on a weekend: " . $dt2->day_name;
    my $stepback = $dt2->dow - 5; # number of days back to Friday
    $dt2->subtract( days => $stepback );

    say "The preceding Friday is $dt2";
} else {
    say "$dt2 is not on a weekend: " . $dt2->day_name;
}

exit;

__END__