anchor.diff: -with (with builtins; {
  -  inherit toFile readFile concatStringsSep unsafeDiscardStringContext
  +with rec {
  +  inherit (builtins)
  +    toFile readFile concatStringsSep unsafeDiscardStringContext
       listToAttrs match head tail toJSON toPath elemAt getAttr length
  -    trace genList isString;
  -  foldl = foldl'; #'
  +    trace genList isString fromJSON getEnv concatLists toString;
  +  foldl = builtins.foldl'; #'
     tracing = x: trace x x;
  -});
  +  for = xs: f: map f xs;
  +  pkgs = import <nixpkgs> {};
  +};
   let
  -  pkgs = import <nixpkgs> {}; 
  -
     mkBuilder = script: toFile "builder.sh" ("source $stdenv/setup\n" + script);
   
     scripts = concatStringsSep " " [
  
positive.code:     for script in ${scripts}; do
        test ! -e $script.orig || cp $script.orig ${dest}/$script
      done
    '';
    make = "make -j $NIX_BUILD_CORES -l $NIX_BUILD_CORES";
  
    skip_tests = [
  
negative.code:       curl
      ];
      builder = mkBuilder ''
        cp -r --no-preserve=all $src/* .
        ./configure
        ${make} DEBUG=1
        test/run -j $NIX_BUILD_CORES '!long' ${skip_tests_filter} || :
  