=word define=
url = "http://www.b.com/item?id=822505"
encoded url = "http%3A%2F%2Fwww.b.com%2Fitem%3Fid%3D822505"

http://www.a.com/fetch?url={encoded url}

url

ex)
http://www.a.com/fetch?url=http%3A%2F%2Fwww.b.com%2Fitem%3Fid%3D822505
->
http://www.b.com/item?id=822505