The best reference I can show for the general programming model was a blog post which is not in G, but was called "Why Concatenative Programming Matters":

http://evincarofautumn.blogspot.com/2012/02/why-concatenativ...

which shows you how graphical diagrams can make sense out of concatenative programs.

If you really want an example, then I will give you this with some caution:

http://team358.org/files/programming/ControlSystem2009-/LabV...

The caution is that LabVIEW views a data source as a sort of continuous input stream, so that it is manipulating individual values at any given time. I would rather view vectors as more fundamental in a spreadsheet language.