sub factorial 
{
   factorial
   my ($n) = @_;
   return 1 if $n == 0;
   return factorial($n-1) * $n;
}

##</code><code>##

sub hanoi 
{
   my ($n, $start, $end, $extra) = @_;
   if ($n == 1) 
   {
      print "Move disk #1 from $start to $end.\n";
   } 
   else 
   {
      hanoi($n-1, $start, $extra, $end);
      print "Move disk #$n from $start to $end.\n";
      hanoi($n-1, $extra, $end, $start);
   }
}

##</code><code>##

Move disk #1 from A to C.
Move disk #2 from A to B.
Move disk #1 from C to B.
Move disk #3 from A to C.
Move disk #1 from B to A.
Move disk #2 from B to C.
Move disk #1 from A to C.