curl https://gist.github.com/bhyde/5383182/raw/gistfile1.txt | bash
That will create a directory on your machine with the example application’s sources, over on Heroku it will build and launch that application, and finally it will open your web browser visiting the home page of the application.
This is all free.
This application is written in Common Lisp. There are lots of nice open source Common Lisp compilers, in this case it’s using Clozure Common Lisp. The sources of the app amount to 16 lines of code. Another few lines implement the hook used by the buildapp to compile the application. Tiny applications like this are made possible thru the excellent build and library support in the modern lisp community; so most of the meat is defining how to use them (i.e. the system definition).
It’s interesting that none of the above installs common lisp on your own machine, nor does it check out the buildpack I built. In total it adds ~200K to your local machine, most of which is the git repository. The actual sources are about 14K, of which the image is 13.
To undo the above you need only delete the directory it creates and destroy the application on heroku:
heroku apps:destroy <name>.