# Module Std.Environment

    module Environment: Environment

    type t = (string, string) Core.Std.List.Assoc.t

    val add : key:string -> data:string -> t -> t

    val find : key:string -> t -> string option

    val find_exn : key:string -> t -> string

    val mem : key:string -> t -> bool

    val remove : key:string -> t -> t

    val import_from_sys : ?default:string -> key:string -> t -> t

    val append_to_path : ?where:[ `Back | `Front ] ->
           key:string -> data:string -> t -> t

    val to_exec_env : t -> string list

    val of_exec_env : string array -> t