anchor.diff:  
     patches = [ ./gc-init.patch ];
   
  -  buildInputs = [ ncurses xlibsWrapper bzip2 zlib openssl spidermonkey_1_8_5 gpm ]
  +  buildInputs = [ ncurses xlibsWrapper bzip2 zlib openssl spidermonkey gpm ]
       ++ stdenv.lib.optional enableGuile guile
       ++ stdenv.lib.optional enablePython python
       ++ stdenv.lib.optional enablePerl perl
  
positive.code:   enableGuile        ? false,                                         guile ? null
  , enablePython       ? false,                                         python ? null
  , enablePerl         ? (stdenv.hostPlatform == stdenv.buildPlatform), perl ? null
  , enableSpidermonkey ? (stdenv.hostPlatform == stdenv.buildPlatform), spidermonkey_1_8_5 ? null
  }:
  
  assert enableGuile -> guile != null;
  
negative.code:   ] ++ stdenv.lib.optional enableGuile        "--with-guile"
      ++ stdenv.lib.optional enablePython       "--with-python"
      ++ stdenv.lib.optional enablePerl         "--with-perl"
      ++ stdenv.lib.optional enableSpidermonkey "--with-spidermonkey=${spidermonkey}"
      ;
  
    meta = {
  