gistfile1.txt

Call
  = id:ID params:Params+ {
      var result = {
            type: "var",
            name: id
          };

      for (var i = 0; i < params.length; i++) {
        result = {
          type:   "call",
          expr:   result,
          params: params[i]
        };
      }

      return result;
    }

Params
  = "(" id:ID ")" { return id; }

ID
  = [a-z]