Operations on URL-style encodings.
module Url: sigval escape : string -> string"%HX"
      URL-escaping format.val unescape : string ->
       error:(string -> 'error) ->
       (string, 'error) Biocaml_internal_pervasives.Result.t"%HX" escaped characters to a normal
      string. In case of error, the string is passed to the ~error parameter
      and the function returns its result.end