#!/usr/bin/perl -w 
use strict;
use DateTime;

my $date = q{20060911};
my $year = substr( $date, 0, 4 );
my $month = substr( $date, 4, 2 );
my $day = substr( $date, 6, 2 );
print DateTime->new( year => $year, month => $month, day => $day )->week_number;