#!c:\perl\bin\perl.exe -w
use strict;
use warnings;

#  This subroutine, given a set of values, should return the standard deviation.

sub standard_deviation {
 my $mean = 0;
 my $sample_size;
 my @differences;
 for (@_) { $mean = $mean + $_; }
 $sample_size = scalar(@_);
 $mean = $mean/$sample_size;
 for (@_) { @differences = (@differences, (($_-$mean)*($_-$mean))); }
 my $standard = 0;
 for (@differences) { $standard = $standard + $_; }
 $standard = sqrt($standard/$sample_size);
 return $standard;
}

my $stddev;
my @values;

@values = (22, 17, 29, 39, 20, 32);

$stddev = standard_deviation(@values);

print "The standard deviation is $stddev.";