Select Code to Download

my ($cnt, $sum, $squ);
while (my ($d) = $iter->()) {
...
my $mean = $sum / $cnt;
my $var = $squ + -2*$mean*$sum + $mean*$mean*$cnt;
my $std  = sqrt($var/$cnt);

my $std  = sqrt($squ/$cnt - $mean*$mean);