#!perl
use strict;

my @data = (10,7,5,10,50,70,75,72,79,80);
my @arr = sort {$a<=>$b} @data;
my $diff = 2; # group closeness

my @avg; #[count,sum]
my @grp;
my $g=0;

for my $i (0..$#arr){
  my $val = $arr[$i];
  #print "value $val\n";
  if ($i == 0){
	push @{$grp[$g]},$val;
	$avg[$g] = [1,$val];
  } else {
    #work out new average with this element
    my ($n,$sum) = @{$avg[$g]};
	#print "count $n sum $sum\n";
    my $avg = $sum/$n;
	my $new_avg = ($sum+$val)/($n+1);
	if (abs($new_avg - $avg) < $diff){
	  # join group
	  push @{$grp[$g]},$val;
	  $avg[$g] = [$n+1,$sum+$val];
	} else {
	  # start new group
	  ++$g;
	  push @{$grp[$g]},$val;
	  $avg[$g] = [1,$val];
	}
  }
}

for (@grp) {
  print join ',',@$_,"\n";
}