doc: update matcher configuration documentation

docs/content/ref/proxy.matcher.md

@@ -8,6 +8,17 @@ title: "proxy.matcher"
 * `prefix`: prefix matching
 * `glob`:  glob matching
 
+When `prefix` matching is enabled then the route path must be a 
+prefix of the request URI, e.g. `/foo` matches `/foo`, `/foot` but 
+not `/fo`.
+
+When `glob` matching is enabled the route is evaluated according to
+globbing rules provided by the Go [`path.Match`](https://golang.org/pkg/path/#Match)
+function.
+
+For example, `/foo*` matches `/foo`, `/fool` and `/fools`. Also, `/foo/*/bar`
+matches `/foo/x/bar`.
+
 The default is
 
     proxy.matcher = prefix