how to append to the requests to origin

["Evuraan::ഏവൂരാന്‍" <evuraan@xxxxxxxxx>]

Greetings,

I've squid running in non-transparent mode. On a MISS, when it makes
requests to the origin, how can something else be passed along with
that request? Like a custom signature header? %{Foobar}i or even
somehting like:

http.setHeader("X-Pew-Pew:Blah-blah-1")

thx.!