To appeal as a commercial product, Caché implements support for object-oriented programming, a macro preprocessing language, embedded SQL for ANSI-standard SQL access to M's built-in database, procedure and control blocks using C-like brace syntax, procedure-scoped variables, and relaxed whitespace syntax limitations.
Thus, editing a global variable is making permanent and immediate changes to a system-universal database (which survives reboots, etc.).
Variables, private and public, may be single elements or complete multi-dimensional arrays.
The great majority of Caché's feature-set is inherited from the ANSI MUMPS standard.
Then in Caché Terminal (assuming you wrote the hello routine to the SAMPLE namespace): [1] Then in Caché Terminal (assuming you wrote the User.Helloworld Class to the SAMPLE namespace):