Add speaker notes for pattern-matching/destructuring-arrays.md (#346)

src/pattern-matching/destructuring-arrays.md

@@ -5,3 +5,26 @@ You can destructure arrays, tuples, and slices by matching on their elements:
 ```rust,editable
 {{#include ../../third_party/rust-by-example/destructuring-arrays.rs}}
 ```
+
+<details>
+
+Destructuring of slices of unknown length also works with patterns of fixed length.
+
+```rust,editable
+fn main() {
+    inspect(&[0, -2, 3]);
+    inspect(&[0, -2, 3, 4]);
+}
+
+#[rustfmt::skip]
+fn inspect(slice: &[i32]) {
+    println!("Tell me about {slice:?}");
+    match slice {
+        &[0, y, z] => println!("First is 0, y = {y}, and z = {z}"),
+        &[1, ..]   => println!("First is 1 and the rest were ignored"),
+        _          => println!("All elements were ignored"),
+    }
+}
+```
+
+</details>