I went and looked at the Advanced Perl Programming example of using swig and gd to make a Fractal perl module. Just to learn about swig, I worked the example out. There are some tricks you need to work thru, since the swig docs are erratic, and the APP example has an error between it's header and c file. Anyways, here are the steps and files to create Fractal.pm with gd and swig. I modified the Advanced Perl Programming example to use Png instead of Gif. Check your perl location for the -I
Run these commands in succession:

1)swig -perl5 fractal.i
2)gcc -fpic -c fractal_wrap.c mandel.c -Dbool=char          -I/usr/lib
+/perl5/5.6.0/i586-linux/CORE
3)gcc -shared fractal_wrap.o mandel.o -lgd -o Fractal.so
4)fractal.pl


#fractal.i
############################################
%module Fractal
%{
#include "mandel.h" 
%}
%include "mandel.h"
##############################################

#mandel.c
#############################################
#include <math.h> 
#include <stdio.h> 
#include <gd.h> 
#include "mandel.h" 
typedef struct {
double r, i;
} complex;

int draw_mandel (char *filename,
int width, int height,
double origin_real,
double origin_imag,
double range,
double max_iterations)
{
complex    origin;
int        colors[51], color, white, x, y, i;
FILE       *out;
gdImagePtr im_out;

origin.r = origin_real;  /* Measured from top-left */
origin.i = origin_imag;

if (!(out = fopen(filename, "wb"))) {
fprintf(stderr, "File %s could not be opened\n");
return 1;
}

im_out = gdImageCreate(width, height); /* Create a canvas */
/* Allocate some gray colors. Start from black, and increment r,g,b 
values uniformly. This has the effect of varying the luminosity, 
while keeping the same hue. 
(Black = 0,0,0 and white = 255, 255,255 */

for (i = 0; i < 50; i++) {
color = i * 4;
colors[i] = gdImageColorAllocate(im_out, color,color,color);
}
white = gdImageColorAllocate(im_out, 255,255,255);
/* For each pixel on the canvas do ... */
for (y = 0; y < height; y++) {
for (x = 0; x < width; x++) {
complex z, c ;
int  iter;
/* Convert the pixel to an equivalent complex number c, 
given the origin and the range. The range acts like an 
inverse zoom factor.*/

c.r = origin.r + (double) x / (double) width * range;
c.i = origin.i - (double) y / (double) height * range;

/* Examine each point calculated above to see if repeated 
substitutions into an equation like z(next) = z**z + c 
remains within a definite boundary. 
If after <max_iterations> iterations it still hasn't gone 
beyond the white area, it belongs to the Mandelbrot set. 
But if it does, we assign it a color depending on how 
far the series wants to jump out of bounds*/
color = white;
z.r = z.i = 0.0; /* Starting point */
for (iter = 0; iter < max_iterations; iter++) {
double dist, new_real, new_imag;
/*calculate  z = z^2 + c */
/* Recall that z^2  is a^2 - b^2 + 2abi, if z = a + bi, */
new_real = z.r * z.r - z.i * z.i + c.r;
new_imag = 2 * z.r * z.i + c.i;
z.r = new_real; z.i = new_imag;
/* Pythagorean distance from 0,0 */
dist = new_real * new_real + new_imag * new_imag;
if (dist >= 4) {
/* No point on the mandelbrot set is more than 2 units 
away from the origin. If it quits the boundary, give 
that 'c' an interesting color depending on how far 
the series wants to jump out of its bounds */
color = colors[(int) dist % i];
break;
}
}
gdImageSetPixel(im_out, x,y, color);
}
}
gdImagePng(im_out,out);
fclose(out);
return 0;
}
############################################

#mandel.h
#########################################
extern int
draw_mandel (char *filename,
             int width, int height,
             double origin_real, double origin_imag,
             double range, double max_iterations);

######################################

#fractal.pl
#######################################
#!/usr/bin/perl
use Fractal;
Fractal::draw_mandel('mandel.png', 300, 300, -1.5, 1.0,2.0, 20);
 # ########### file ,  width, height, origin x,y  max-iterations

#########################################
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