As cyocum correctly deduced, your problem is that you're setting the proxy to the configuration file.

That file is Javascript, which is supposed to be executed by the browser on a URL-by-URL basis to determine which proxy to use for which URL.

LWP does not (and probably never will) support that.

You need to read the file, understand it, and select a proxy from it yourself: $ua->proxy('http','proxyslb.tau.ac.il:8080'); for example.