recursive argument matching

let splitIncludesAndExcludes =
    searchPatterns |> 
        Seq.fold(fun (acc,collecting) next -> 
            match next with
            | IncludeKey -> (acc, Include)
            | ExcludeKey -> (acc, Exclude)                                       
            | next -> 
                match collecting with
                | Skip -> (acc, collecting)
                | Include ->                             
                    ({ acc with Includes = next::acc.Includes }, Include)
                | Exclude -> 
                    ({ acc with Excludes = next::acc.Excludes }, Exclude))
            ({ Includes = []; Excludes = []; }, Skip)
    |> fst