let l1 = [1; 0; 1; 1]                                                                             

let l2 = [0; 0; 1; 0]

​

let sumMatches ns ms = List.fold2 (fun acc n m -> acc + if n = m then 1 else 0) 0 ns ms

​

sumMatches l1 l2  |> printfn "Count = %i"