Just a snippet of test wrote against an unreleased branch of CommandLine

cmdline_test.fs

open System
open System.Reflection
open CommandLine
open CommandLine.Text

[<assembly: AssemblyCopyright("Copyright (c) 2013 Giacomo Stelluti Scala playing with FSharp")>]
do()

type options() =
    [<Option(HelpText = "Let your program talk a lot.")>]
    member val verbose = false with get, set
    [<Option(HelpText = "A file not used in this program.")>]
    member val filename = "" with get, set
    [<ParserState>]
    member val parserState : ParserState = null with get, set

[<EntryPoint>]
let main argv = 
    let conf  =
        let mutable sett = new ParserSettings()
        sett.DynamicAutoBuild <- true
        sett.HelpWriter <- Console.Error
        sett
    use parser = new CommandLine.Parser(conf)
    let opts = 
        let onExit = new Action(fun() -> printfn "fail!")
        parser.ParseArguments<options>(argv, onExit)
    printfn "%A %A" opts.verbose opts.filename
    0