At the bottom of the reference for world.Export() is this little blurb:
"Note that the HTTP request is submitted using the GET method as opposed to the POST method. Support for POST may be added in the future."

Has any support been added to handle POST yet? :)

In response to Nadrew
I believe this can be done through browser elements. Doing so without user interaction on the other hand, might require an external web server with PHP installed.