It is frustrating that the example in the manual doesn’t build, especially when only small changes are required to default.nix: let pkgs = import {}; in pkgs.stdenv.mkDerivation { name = “hello-2.1.1”; builder = ./builder.sh; src = pkgs.fetchurl { url = ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz; sha256 = “1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465”; }; perl = pkgs.perl; }