this is a url: http://www.example.com/foo-bar
 key   0:13  ^-----------^                                  this is a url
 url  15:45                 ^----------------------------^  http://www.example.com/foo-bar
 val  15:45                 ^----------------------------^  http://www.example.com/foo-bar
pair   0:45  ^-------------------------------------------^  this is a url: http://www.example.com/foo-bar