foreach my $subrow (keys %pair1data) { $zee1 = ( ( $pair1data{$subrow} - $submean1 ) / $substddev1 ); $zee2 = ( ( $pair2data{$subrow} - $submean2 ) / $substddev2 ); $sigma += ( $zee1 * $zee2 ); $datasetcounter ++; } $r = ( $sigma / ( $datasetcounter - 1 ) ); return $r;