anchor.diff:   
           environment = {
   	  extraPackages = [
  -	    pkgs.firefoxWrapper
   	    pkgs.scrot
   	  ];
   	};
  
positive.code:     webserver = 
        {config, pkgs, ...}:
        {
          services = {
  	  portmap = {
  	    enable = true;
  
negative.code:         };
  	
  	environment = {
  	  extraPackages = [ pkgs.pythonPackages.trac pkgs.subversion ];
  	};
        };
        
  