in reply to Fractal structure index puzzle
you might want to have a look to a recent article in the Free Software Magazine on Generating Cool Fractals. There, you would find a Benchmark showing execution time for computing a Mandelbrot fractal image using different languages. It took about 200 seconds with gcc and g77 for 2000 points and 1000 iterations. For the same image using PDL, it took about 650 seconds. If you main concern is execution time, then I would think about using C. If you definitely want to do it in Perl, then PDL is your best bet. However, you would have to learn how to use matrix operations to avoid the use of loops as much as you can.