push @{$r{join ' ' x 8, @F[0..3]};}, [@F[4, 6]];
	{
		foreach my $k (keys %r) {
			my($x, $y);
print "\$r{\$k};", $r{$k};
print "\@{\$r{\$k};}", @{$r{$k};};
			map {$x += $$_[0]; $y += $$_[1];
print "\$_='$_'", "SS_[0]=$$_[0]", "SS_[1]=$$_[1]", "x=$x", "y=$y";
            } @{$r{$k};};
			my @g = split(/\s+/,$k);
			print OUT "$g[0]\t@g[1]\t@g[2]\t@g[3]\t", $x / scalar(@{$r{$k};}), "\t$y\n";
		}
	}

##</code><code>##

   $k;         # == "1  136  G   A" with more spaces
   $r{$k};     # == [ [1,6], [1,9] ]  == referenece to an array of array-refs
   @{$r{$k}};  # == ( [1,6], [1,9] )  == array of array-refs
   map {} @    # for each element in the @ array, run the {} block

   # First element of @ is the first ref to a pair-array:
   $_;         # = [1,6] == array ref
   $$_;        # = (1,6) == array
   $$_[0];     # = 1 == first element of array (1,6) or arrayref [1,6]
   $$_[1];     # = 6

   # Second element of @ is the next ref to a pair-array
   $_;         # = [1,9]
   $$_[0];     # 1
   $$_[1];     # 9