(Blah blah HTML)
<IMG SRC = "http://www.server.com/cgi-bin/image.pl?iwant=5
(blah blah HTML)

##</code><code>##

#!/usr/bin/perl
use POSIX;
my $path = "/path/to/images";
my $imagereq = param('iwant');
#If you don't give an image, it assumes you
#want image 0, the defaut image. 
unless($imagereq) { $imagereq = 0; }


#If the image you requested exists (all are JPEG), then
#we set our path to reflect this
if(-e "$path/$imagereq".".jpg") {
$path = "$path/$imagereq".".jpg"; 
} 

#Otherwise, we give them an special image
else { $path = "$path"."404.jpg"; }

#Open the image and 'print' it, which the browser
#is quite happy to accept and display as an image
open IMAGE, "$path" or die "ACK! $!";
print "Content-type: image/jpeg\n\n";
binmode STDOUT;
while(<IMAGE>) {
print STDOUT $_;
}