anchor.diff:    src = fetchurl {
       urls = tarballUrls version;
       hashOutput = false;
  -    sha256 = "d4f3cd31c001fd0ed52832d4fbfbdfeaa38ad541c182f80ff8fdf87324a6a9f2";
  +    sha256 = "d1119785e746d46a8209d28b2de404a57f983aa48670f4e225531d3bdc175551";
     };
   
     buildInputs = [
  
positive.code:     srcVerification = fetchurl rec {
        inherit (src) outputHashAlgo;
        failEarly = true;
        urls = tarballUrls "4.2.0";
        outputHash = "d4f3cd31c001fd0ed52832d4fbfbdfeaa38ad541c182f80ff8fdf87324a6a9f2";
        pgpsigUrls = map (n: "${n}.sig") urls;
        pgpKeyFingerprint = "D196 7C63 7887 1317 7D86  1ED7 DF59 7815 937E C0D2";
      };
  
negative.code: }:
  
  let
    version = "4.2.1";
  
    tarballUrls = version: [
      "mirror://gnu/gawk/gawk-${version}.tar.xz"
  