管道 Debug.log

在執行時，以下內容將在控制檯中顯示 url 列表並繼續計算

payload =
    [{url:..., title:...}, {url=..., title=...}]

main = 
    payload
        |> List.map .url -- only takes the url
        |> Debug.log " My list of URLs" -- pass the url list to Debug.log and return it
        |> doSomething -- do something with the url list