Ocaml where and how to define a function that only returns a value

I have the following code

let mymain origarg =   let results = helperfunc origarg in   (results, origarg)let rec helperfunc newarg =   match newarg with  | [] -> []  | h::t -> h :: helperfunc (someotherfunc t origarg)

origarg is a list. How do I write a function that can supply the unmodified origarg to my helperfunc on every recursive call?