#!/C:\Perl64\bin\perl.exe
use strict;
use warnings;

my @numlist     = qw(2 4 4 4 5 5 7 9);
my $numlist_avg = avg(@numlist);
my @cands;
my @abvlist = abv(@numlist);
my $sigma   = std_dev(@numlist);
my @squares;
my $len = $#numlist + 1;

print "The count of numbers in \@numlist is ", $#numlist + 1, "\.\n";
print "The total of \@numlist is ",        total(@numlist), "\.\n";
print "The mean average of \@numlist is ", avg(@numlist),   "\.\n";
print "The list of numbers in \@numlist over the mean is  ", join(',', @abvlist), "\.\n";
print "The list of numbers that will probably be duplicates in \@numlist over the mean is  ",
  join(',', abv(@numlist)), "\.\n";
print "The standard deviation of numbers in \@numlist is ", $sigma, "\.\n";

sub total
{
    my $endresult = 0;
    foreach my $x (@numlist) {
        $endresult += $x;
    }
    return $endresult;
}

sub avg
{
    my $len1 = $#numlist + 1;
    return total(@numlist) / $len1;
}

sub abv
{
    foreach my $cand (@numlist) {
        if ($cand > $numlist_avg) {
            push(@cands, $cand);
        }
    }
    return @cands;
}

sub std_dev
{
    my $len2 = $#numlist + 1;
    foreach my $num (@numlist) {
        my $step1 = $num - $numlist_avg;
        my $step2 = $step1 * $step1;
        push(@squares, $step2);
    }
    my $start2 = 0;
    foreach my $num2 (@squares) {
        $start2 += $num2;
    }
    return sqrt($start2 / $len2);
}