anchor.diff:        '';
       };
   
  +    system.replaceRuntimeDependencies = mkOption {
  +      default = [];
  +      example = lib.literalExample "[ ({ original = pkgs.openssl; replacement = pkgs.callPackage /path/to/openssl { ... }; }) ]";
  +      type = types.listOf (types.submodule (
  +        { options, ... }: {
  +          options.original = mkOption {
  +            type = types.package;
  +            description = "The original package to override.";
  +          };
  +
  +          options.replacement = mkOption {
  +            type = types.package;
  +            description = "The replacement package.";
  +          };
  +        })
  +      );
  +      apply = map ({ original, replacement, ... }: {
  +        oldDependency = original;
  +        newDependency = replacement;
  +      });
  +      description = ''
  +        List of packages to override without doing a full rebuild.
  +        The original derivation and replacement derivation must have the same
  +        name length, and ideally should have close-to-identical directory layout.
  +      '';
  +    };
  +
     };
   
   
  
positive.code:       perl = "${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/lib/perl5/site_perl";
    } else throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failed)}");
  
  
  in
  
  
negative.code:   # kernel, systemd units, init scripts, etc.) as well as a script
    # `switch-to-configuration' that activates the configuration and
    # makes it bootable.
    baseSystem = showWarnings (
      if [] == failed then pkgs.stdenv.mkDerivation {
        name = "nixos-${config.system.nixosVersion}";
        preferLocalBuild = true;
  