Thanks for your reply, Chip. It turns out the problem was in my statements to print the image. For some reason they'd only work if the cookie was also set but not if it wasn't. I replaced the last three lines with the following and it works now. I don't have enlightenment but I do have results, so I'll go with that.

my $image = 'logo.gif'; 
open(IMAGE, "<$image") or die "cannot open image file: $!"; 
my $no_bytes = (stat ($image))[7]; 
print "Content-type: image/gif\n"; 
print "Content-length: $no_bytes\n"; 
print "Pragma: no-cache\n\n"; 
print <IMAGE>; 
close(IMAGE) or die "cannot close image file: $!";
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