[Learning Mode] Discussion: building up to Pattern Matching

@MatthijsBlom suggested the following concept graph, which is a good starting point for building up to a basic understanding of proper pattern matching in Haskell.

```
|
Simple Pattern Matching
/ | \
Maybe Either ... (tuples, lists?)
\ | /
Algebraic Data Types
("custom types")
|
Pattern Matching Proper
|
```

I'd like to start the discussion by looking at some sample code that demonstrates the end point, _Pattern Matching Proper_. It doesn't have to relate to any exercise or story, rather it's a way to make sure that everyone involved understands where we're trying to get to.

@MatthijsBlom I know you've been thinking a lot about this over the past couple of weeks. Would you be willing to write a few (maybe 10 or so?) lines of code to illustrate _Pattern Matching_?