Oberon is a programming language created by Professor Niklaus Wirth, the father of Pascal and Modula. It is very Modula-like in its syntax, but offers an interesting feature which is only making its way in today's world: exportability of procedures.
Imagine that for your program you create a PNG viewer procedure and that you export it: any program on the system will be able to view PNG files! That's reusability at most. Granted this is possible currently on other systems (see for example the use made by Galeon of the Mozilla engine), but mechanisms in Oberon are far better and simpler than most of what currently exists.