how to access "get" values in url from inside form code

I am trying to retrieve "get" values from a url and use them inside a Form's code.

For example from the following url:
http://creator.zoho.com/<user name>/<app name>/form-perma/<form name>/key=30409000000057085

I need to get the value 30409000000057085 and put it in a drop down list.

The documentation on the following page says: "Note: The default field values will be available in the form's on load action."
http://help.creator.zoho.com/Functionality-based-URLs.html#To_edit_individual_records_by_passing_record_id_in_the_URL

I could not find a way to get the values, via the script-builder or otherwise. Can anyone help?