#!/usr/bin/perl 

use strict;
use warnings;
use Statistics::Basic qw(:all);

use constant HITS  => qw(2378 4024 9696 
                      7314 7710);
use constant SALES => qw(310.94 315.88 514.15 
                      500.18 610.37);

my $cov = (HITS, SALES);

print
"The covariance is : $cov\n";