Executing 
The Playground lets you try out the rFun programming language in your browser without having to install anything. When you click "Run" the program is sent to the server where it is executed and the result is returned.
At the rFun Playground the interpreter have been implemented by Michael Kirkedal Thomsen, while the webpage have been created by Claus Skou Nielsen and Michael Budde.
You can load example programs by clicking on the Examples dropdown in the menu and selecting an example which will then be loaded into the text area.
The code in the text area can be run by pressing the Run button in the menu and the output will appear in a seperate pane below the text area.
If the program fails, the error will be show in red in the output pane. The error will explain you what went wrong and in which line, and give you useful information about the program state, for example it prints the variable store when the error occured.