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perl/Examples/Chap5/factorial-1

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+
+
+###
+### factorial1
+###
+
+## Chapter 5 section 4.2
+
+sub factorial {
+  my ($n, $product) = @_;
+  $product = 1 unless defined $product;
+  return $product if $n == 0;
+  return factorial($n-1, $n * $product);
+}