Hey this is a great web server example! Instead of commenting it out to enable or disable you can actually turn it into a full module. Check out this example of a nix module. Basically, you can take your code you pasted and put it under the config set. Then create an option to enable that set of code. Now you can always have this nix file imported, but enable the option only when you need it with another declaration. Really, that's how all the declarations work you're just getting the nix files from github and nixpkgs.