anchor.diff: -{ stdenv, fetchurl, autoconf, automake, pkgconfig
  +{ gcc9Stdenv, fetchurl, autoconf, automake, pkgconfig, lib
   , perl, flex, bison, readline, libexif
   , x11Support ? true, SDL
   , svgSupport ? true, inkscape
  
positive.code:     ++ optional jpegSupport libjpeg
      ++ optional pngSupport libpng;
  
    NIX_CFLAGS_COMPILE = stdenv.lib.optionalString x11Support "-lSDL";
  
    meta = with stdenv.lib; {
      description = "A lightweight, highly customizable and scriptable image viewer";
      longDescription = ''
        FIM (Fbi IMproved) is a lightweight, console based image viewer that aims
  
negative.code: 
    nativeBuildInputs = [ autoconf automake pkgconfig ];
  
    buildInputs = with lib;
      [ perl flex bison readline libexif ]
      ++ optional x11Support SDL
      ++ optional svgSupport inkscape
  