Listing 1. The Baseline Implementation of std_dev

sub mean {
  my $result;
  foreach (@_) { $result += $_ }
  return $result / @_;
}


sub std_dev {
  my $mean = mean(@_);
  my @elem_squared;
  foreach (@_) {
    push (@elem_squared, ($_ **2));
  }
  return sqrt( mean(@elem_squared) - ($mean ** 2));
}