Your readdir is failing. The first line needs to do something if it's going to be effective. You have it has:

opendir BUFFER, "images/" or "Serious Headache! $!";
[download]

But you probably want to do:

opendir BUFFER, "images/" or print "Serious Headache! $!";
[download]

You can also make it a fatal error by using die "Serious Headache! $!" and use CGI::Carp(fatalsToBrowser).. Hope that helps. Also, you know what they say, while in Rome, make sure you have read and executable permissions on the Romans.

    --jb