如何在F#中获取逗号后的数字

let input = "abc,123,def"

let getNumbersAfterComma (str: string) =
    let mutable flag = false
    let mutable result = []
    let charArray = str.ToCharArray()
    
    List.fold (fun acc c ->
        if flag then
            match System.Int32.TryParse(c.ToString()) with
            | true, num -> result <- num :: result
            | _ -> ()
        if c = ',' then
            flag <- true
        acc
    ) () charArray
    
    List.rev result

let numbersAfterComma = getNumbersAfterComma input
printfn "%A" numbersAfterComma