I don't know how to add some string to itself in loop.

```
let parameters = [| [| ("name", "fdjks"); ("value", "dsf") |]; [| ("name", "&^%"); ("value", "helo") |] |] ;;
let boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW";;
let body = "";;

for x = 0 to (Array.length(parameters) : int)-1 do
    let (_, paramName) = parameters.(x).(0) in
    let (_, paramValue) = parameters.(x).(1) in
    body = body ^ "--" ^ boundary ^ "\r\n" ^ "Content-Disposition:form-data; name=\"" ^ paramName ^ "\"\r\n\r\n" ^ paramValue ;
    print_endline(body)
done;;

```

but this gives error..
Any way to do this......?