#compdef _label label
_label() {
    local line state

    _arguments -C \
               "1: :->cmds" \
               "*::arg:->args"
    case "$state" in
        cmds)
            _values "label command" \
                    "add[Create or overwrite a label.]" \
                    "ls[List existing labels.]" \
                    "get[Fetch the location of a label.]" \
                    "rm[Delete a label.]"
            ;;
        args)
            case "$line[1]" in
                rm|get)
                  _goto  # get the labels as completions
                  ;;
            esac
            ;;
    esac
}