Error: 500 Status read failed: Unknown error
Client-Date: Tue, 12 May 2015 15:19:46 GMT
Client-Warning: Internal response
This error was generated on the client side by LWP::UserAgent (see last line), not by the server. It seems the communication with the HTTPS server failed. Are you sure your LWP installation supports HTTPS? Try connecting to https://www.google.com/ or similar.
Maybe the HTTPS server uses a self-signed certificate? (But that should give a different error message ...)
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)