If you are using a vanilla installation of Perl and getting this problem from google, I see two possibilities:

1. You have some other piece of local software -- say a local proxy -- that is interfering.

   I suspect that the error text you are receiving is spurious. Ie. an extended error code left over from an earlier failing operation that is only showing up when you print error message after the (legimate) 500 error from the get.

   You might be able to verify that by setting $^E = 0 before you do the GET. (Untested)

2. You have done so much automated downloading from google that your IP has risen above their parapet and they are now restricting your IP to connections that use browser user-agent strings.

   Ie. They are blocking requests that aren't from browsers.

   You could test this theory by setting the user-agent string in LWP to something that looks like a browser.

   But beware; because they will soon detect that you are emulating a browser and apply tighter restrictions if not an outright ban if you do this a lot.

Those are my best guesses; its hard to try and help given I cannot reproduce the problem.