Often times webservers, or scripts, will be run in some sort of jail/chroot environment, or other security sandbox. You might try something like the following, to see what is going on.

#!/usr/bin/perl
use CGI;
use Cwd;
my $q = new CGI;
print $q->header();
print "<pre>\n";
printf("cwd: %s\n", getcwd);
printf("/var/www/images: %s\n", -d "/var/www/images" ? 'is a directory
+' : 'is not a directory');
printf("/var/www/images: %s\n", -r "/var/www/images" ? 'readable' : 'n
+ot readable');
printf("</pre>");
[download]

This won't solve your problem, but might point you in the right direction.