proxy autoconfig

Anybody know how to debug an autoconfig proxy file?

I made a file, proxy.pac, and put it on
/var/www/html on 192.168.5.15

In the httpd.conf I put

AddType application/x-ns-proxy-autoconfig .pac

and restarted httpd.

My proxy.pac is simple:

function FindProxyForURL(url, host) {

     if (isInNet(host, "10.0.0.0",  "10.255.255.255"))    {

        return "PROXY 192.168.5.15:8001";

     }

     // All other requests are direct

     return "DIRECT";

  }

And things seem to work OK for anything other than 10.0.0 networks.  I put that into my Firefox
proxy settings for Automatic Proxy Configuration URL: http://192.168.5.15/proxy.pac
and reloaded.

However, it still does not work for 10.0.0 addresses.  When I specify 192.168.5.15 port 8001 manually
it works OK but then everything goes through there and I need only the 10.0.0 ones to go through.

Anyone know either how to debug or what I am doing wrong?
Live HTTP Headers does not show anything.  Nor does the _javascript_ console.