state that state variables are shared between threads

doc/Language/variables.pod

@@ -578,6 +578,18 @@ Please note that many operators come with implicit binding, what will lead to ac
     f for 1..3;
     dd @a; # «Array $var = $[:k1(3), :k2(3), :k3(3)]»
 
+All state variables are shared between threads. The result can be undesired or
+dangerous.
+
+    sub code(){ state $i = 0; say ++$i; $i }; 
+    await 
+        start { loop { last if code() >= 5 } },
+        start { loop { last if code() >= 5 } };
+
+    # OUTPUT«1␤2␤3␤4␤4␤3␤5␤»
+    # OUTPUT«2␤1␤3␤4␤5␤»
+    # many other more or less odd variations can be produced
+
 =head3 The C<$> Variable
 
 As well as explicitly declared named state variables C<$> can be used