March 2014 update

Task/Averages-Simple-moving-average/Perl/averages-simple-moving-average.pl

@@ -1,7 +1,18 @@
-sub sma ($)
- {my ($period, $sum, @a) = shift, 0;
-  return sub
-     {unshift @a, shift;
-      $sum += $a[0];
-      @a > $period and $sum -= pop @a;
-      return $sum / @a;}}
+sub sma_generator {
+    my $period = shift;
+    my (@list, $sum);
+
+    return sub {
+        my $number = shift;
+        push @list, $number;
+        $sum += $number;
+        $sum -= shift @list if @list > $period;
+        return $sum / @list;
+    }
+}
+
+# Usage:
+my $sma = sma_generator(3);
+for (1, 2, 3, 2, 7) {
+    printf "append $_ --> sma = %.2f  (with period 3)\n", $sma->($_);
+}