let post url ?form headers =
let hv = hv_empty () in
(match form with
| None -> ()
| Some xs -> List.iter (fun (k, v) -> hv_set hv k (sv_of_string v)) xs);
let args =
sv_of_string url :: hashref hv ::
List.fold_right (fun (k, v) rest ->
sv_of_string k :: sv_of_string v :: rest)
headers [] in
new http_request (call ~fn:"POST" args)