let
  fromEnv = var: def:
    let val = builtins.getEnv var; in
    if val != "" then val else def;
in {
  perl = "@perl@";
  shell = "@shell@";
  coreutils = "@coreutils@";
  bzip2 = fromEnv "NIX_BZIP2" "@bzip2@";
  tar = "@tar@";
  tr = "@tr@";
  curl = "@curl@";
  nixBinDir = fromEnv "NIX_BIN_DIR" "@bindir@";
}