$ cat server.scm 
(use spiffy simple-directory-handler)

(handle-directory simple-directory-handler)

(start-server)

$ mkdir web
$ cd web
$ ln -s foo foo
$ cd ..
$ csi -s server.scm &
[1] 6379

$ wget http://localhost:8080
--2012-10-24 17:32:45--  http://localhost:8080/
Resolving localhost... ::1, 127.0.0.1
Connecting to localhost|::1|:8080... failed: Connection refused.
Connecting to localhost|127.0.0.1|:8080... connected.
HTTP request sent, awaiting response... [Wed Oct 24 17:32:45 2012] "GET http://localhost:8080/ HTTP/1.0" Error: (file-exists?)
system error while trying to access file
"./web//foo"

        Call history:

        display   
        spiffy#root-path          
        make-pathname     
        simple-directory-handler#simple-directory-dotfiles?       
        directory         
        sort      
        fold      
        spiffy#root-path          
        make-pathname     
        make-pathname     
        directory?        
        file-exists?      
        k695701   
        g699700   
        spiffy#handle-exception   
        with-output-to-string           <--


500 Internal Server Error
2012-10-24 17:32:45 ERROR 500: Internal Server Error.