From iA wiki
See also: Operating System
REBOL was designed over a 20-year period by Carl Sassenrath, the system architect responsible for the world's first multi-tasking multimedia operating system, the Commodore Amiga OS. The first implementation of REBOL (pronounced like "rebel yell") was released in 1997 to a small group of users running on three operating systems, and today REBOL has grown to reach more than 1,000,000 users running on more than 40 OS platforms.
REBOL is not a traditional computer language like C, BASIC, or Java. Instead, REBOL was designed to solve one of the fundamental problems in computing: the exchange and interpretation of information between distributed computer systems. REBOL accomplishes this through the concept of relative expressions (which is how REBOL got its name as the Relative Expression-Based Object Language). Relative expressions, also called "dialects", provide greater efficiency for representing code as well as data, and they are REBOL's greatest strength. For example, REBOL can not only create a graphical user interface in one line of code, but it can also send that line as data to be processed and displayed on other Internet computer systems around the world.
It's the best thing in IT I got my hands on in the last 5 years. I needed three attempts until I realized the power of it. So be prepared to see some real new stuff and improve your knowledge. Script Library (many user-contributed examples): http://www.rebol.org
See also http://rebolnuts.free.fr