diff --git a/CMakeLists.txt b/CMakeLists.txt
index d60ed03..a395cc7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.16)
-project(fun VERSION 0.21.0 LANGUAGES C)
+project(fun VERSION 0.21.1 LANGUAGES C)
 
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_C_STANDARD_REQUIRED ON)
diff --git a/examples/tcp_http_get_class.fun b/examples/tcp_http_get_class.fun
index 9cfd10b..b40c63d 100755
--- a/examples/tcp_http_get_class.fun
+++ b/examples/tcp_http_get_class.fun
@@ -1,3 +1,5 @@
+#!/usr/bin/env fun
+
 /*
  * This file is part of the Fun programming language.
  * https://hanez.org/project/fun/
diff --git a/examples/try_catch_finally.fun b/examples/try_catch_finally.fun
index 37f53ba..1369a5b 100755
--- a/examples/try_catch_finally.fun
+++ b/examples/try_catch_finally.fun
@@ -1,3 +1,5 @@
+#!/usr/bin/env fun
+
 /*
  * This file is part of the Fun programming language.
  * https://hanez.org/project/fun/
diff --git a/examples/try_catch_with_error.fun b/examples/try_catch_with_error.fun
index 0cf05be..5e289aa 100755
--- a/examples/try_catch_with_error.fun
+++ b/examples/try_catch_with_error.fun
@@ -1,3 +1,5 @@
+#!/usr/bin/env fun
+
 /*
  * This file is part of the Fun programming language.
  * https://hanez.org/project/fun/
diff --git a/examples/unix_socket_echo.fun b/examples/unix_socket_echo.fun
new file mode 100755
index 0000000..a95d30e
--- /dev/null
+++ b/examples/unix_socket_echo.fun
@@ -0,0 +1,68 @@
+#!/usr/bin/env fun
+
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2025-10-04
+ */
+
+/*
+ * UNIX domain socket echo demo.
+ * - On Unix-like systems: demonstrates unix_listen + tcp_accept + unix_connect + sock_send/recv.
+ * - On Windows: prints a friendly message and exits (since AF_UNIX is not available here).
+ */
+
+fun server_thread(listen_fd)
+  // Accept a single client, read message, echo back, close.
+  cfd = tcp_accept(to_number(listen_fd))
+  if (cfd <= 0)
+    // accept failed
+    return 0
+  msg = sock_recv(cfd, 4096)
+  // Simple echo prefix
+  _ = sock_send(cfd, join(["echo:", msg], ""))
+  _ = sock_close(cfd)
+  return 1
+
+// Cross-platform guard: Windows sets OS=Windows_NT
+os = env("OS")
+if (os == "Windows_NT")
+  print("UNIX domain sockets are not supported on Windows in this build. Skipping demo.")
+else
+  // Path for the UNIX socket
+  path = "/tmp/fun_unix_echo.sock"
+
+  // Start a UNIX listening socket
+  lfd = unix_listen(path, 1)
+  if (lfd <= 0)
+    print(join(["unix_listen failed at ", path], ""))
+  else
+    // Spawn the server thread which will accept exactly one client
+    tid = thread_spawn(server_thread, lfd)
+
+    // Small delay to ensure the server is accepting
+    sleep(50)
+
+    // Create a client using raw built-ins (no stdlib dependency)
+    cfd = unix_connect(path)
+    if (cfd <= 0)
+      print("unix_connect failed")
+    else
+      // Send a message and read the reply
+      _ = sock_send(cfd, "hello over AF_UNIX")
+      reply = sock_recv(cfd, 4096)
+      print(reply)
+      _ = sock_close(cfd)
+
+    // Join the server thread and close the listening socket
+    _ = thread_join(tid)
+    _ = sock_close(lfd)
+
+/* Expected output:
+echo:hello over AF_UNIX
+*/