Get all sub-directories (See related posts)

    dirs: func [
        {Returns a block of fully qualified subdirectories for the directory.}
        spec  [file!]   "Starting directory"
        block [block!]  "Block to append to"
        /deep           "Recurse sub-directories."
        /local f-spec
    ][
        spec: dirize spec
        foreach file read spec [
            if dir? f-spec: join spec file [
                append block f-spec
                if deep [all-dirs/deep f-spec block]
            ]
        ]
        block
    ]