6.3. Specifying Extensions in Regina In Regina there are three level of extensions. Each independent extension has its own name. Exactly what an independent extension is, will depend on the viewer, but a classification has been done, and is listed at the end of this chapter. At the lowest level are these “atomic” extensions. Then there are some “meta-extensions”. These are collections of other extensions which belongs together in some manner. If you need the extension for creating “buffers” on the stack, it would be logical to use the extension to remove buffers from the stack too. Therefore, all the individual extensions for operations that handle buffers in the stack can be named by such a “meta-extensions”. At the end of this chapter, there is a list of all the meta-extensions, and which extensions they include. At the top is “standards”. These are sets of extensions that makes the interpreter behave in a fashion compatible with some standard. Note that “standard” is used very liberally, since it may refer to other implementations of REXX. However, this description of how the extensions are structured is only followed to some extent. Where practical, the structure has been deviated.