F# Mapping Regular Expression Matches with Active Patterns

I found this useful article on using Active Patterns with Regular Expressions: http://www.markhneedham.com/blog/2009/05/10/f-regular-expressionsactive-patterns/

The original code snippet used in the article was this:

open System.Text.RegularExpressions

let (|Match|_|) pattern input =
    let m = Regex.Match(input, pattern) in
    if m.Success then Some (List.tl [ for g in m.Groups -> g.Value ]) else None

let ContainsUrl value = 
    match value with
        | Match "(http:\/\/\S+)" result -> Some(result.Head)
        | _ -> None

Which would let you know if at least one url was found and what that url was (if I understood the snippet correctly)

Then in the comment section Joel suggested this modification:

Alternative, since a given group may or may not be a successful match:

List.tail [ for g in m.Groups -> if g.Success then Some g.Value else None ]

Or maybe you give labels to your groups and you want to access them by name:

(re.GetGroupNames()
 |> Seq.map (fun n -> (n, m.Groups.[n]))
 |> Seq.filter (fun (n, g) -> g.Success)
 |> Seq.map (fun (n, g) -> (n, g.Value))
 |> Map.ofSeq)

After trying to combine all of this I came up with the following code:

let testString = "http://www.bob.com http://www.b.com http://www.bob.com http://www.bill.com"

let (|Match|_|) pattern input =
    let re = new Regex(pattern)
    let m = re.Match(input) in
    if m.Success then Some ((re.GetGroupNames()
                                |> Seq.map (fun n -> (n, m.Groups.[n]))
                                |> Seq.filter (fun (n, g) -> g.Success)
                                |> Seq.map (fun (n, g) -> (n, g.Value))
                                |> Map.ofS