Improve redirects documentation with advanced regex patterns

fern/snippets/redirects.mdx

@@ -1,9 +1,9 @@
-The `redirects` object allows you to redirect traffic from one path to another. You can redirect exact paths or use dynamic patterns with [`regex`](https://www.npmjs.com/package/path-to-regexp) parameters like `:slug` to handle bulk redirects. You can redirect to internal paths within your site or external URLs.
+The `redirects` object allows you to redirect traffic from one path to another. You can redirect exact paths or use dynamic patterns with [Path-to-RegExp](https://www.npmjs.com/package/path-to-regexp) parameters like `:slug` to handle bulk redirects. You can redirect to internal paths within your site or external URLs.
 
 If your docs are hosted on a subpath (like `buildwithfern.com/learn`), include the subpath in both the source and destination paths. 
 
-
   <CodeBlock title="docs.yml">
+
     ```yml
     redirects:
       # Exact path redirects
@@ -17,11 +17,17 @@ If your docs are hosted on a subpath (like `buildwithfern.com/learn`), include t
         destination: "/new-location"
         permanent: false # Use 307 (temporary) instead of 308 (permanent)
 
-      # Regex-based redirects
+      # Pattern-based redirects
       - source: "/old-folder/:slug" # Matches single segments: /old-folder/foo
         destination: "/new-folder/:slug"   
       - source: "/old-folder/:slug*" # Matches multiple segments: /old-folder/foo/bar/baz 
-        destination: "/new-folder/:slug*"  
+        destination: "/new-folder/:slug*"
+
+      # Named capture groups with regex patterns
+      - source: "/release-notes/:year(\\d{4})-{0}:month(\\d{1,2})"
+        destination: "/docs/release-notes/:year/:month/1"
+      - source: "/api/v:version(\\d+)/:endpoint*"
+        destination: "/api-reference/:version/:endpoint*"
     ```
   </CodeBlock>
 
@@ -41,6 +47,40 @@ If your docs are hosted on a subpath (like `buildwithfern.com/learn`), include t
   `true` or `false` - default is `true`. If `true`, will use the 308 status code which instructs clients/search engines to cache the redirect forever. If `false`, will use the 307 status code which is temporary and is not cached.
 </ParamField>
 
+### Advanced patterns
+
+You can define named capture groups with regex patterns and reuse them in destination URLs:
+
+<CodeBlock title="docs.yml">
+
+```yml
+redirects:
+  # Match 4-digit years
+  - source: "/blog/:year(\\d{4})/:slug*"
+    destination: "/archive/:year/:slug*"
+
+  # Match dates with literal separator
+  - source: "/posts/:year(\\d{4})-{0}:month(\\d{2})-{0}:day(\\d{2})"
+    destination: "/blog/:year/:month/:day"
+
+  # Match numeric IDs only
+  - source: "/user/:id(\\d+)"
+    destination: "/users/:id/profile"
+```
+</CodeBlock>
+
+<Accordion title="Pattern syntax">
+
+| Pattern | Description |
+|---------|-------------|
+| `:name` | Captures a single path segment |
+| `:name*` | Captures zero or more segments |
+| `:name(\\d+)` | Captures digits only |
+| `:name(\\d{4})` | Captures exactly 4 digits |
+| `{0}` | Literal character delimiter between parameters |
+
+</Accordion>
+
 ### Best practices
 
 For optimal site performance, only add redirects when necessary. Avoid using redirects for behavior that Fern already handles automatically, such as 404 handling and version routing.