Improve docs for infix =:=

lib/Language/operators.pod

@@ -958,11 +958,21 @@ types must override method C<WHICH>.
 
 =head2 infix C«=:=»
 
-    proto sub infix:<=:=>(Mu $a is rw, Mu $b is rw) returns Bool:D is assoc<chain>
-    multi sub infix:<=:=>(Mu $a is rw, Mu $b is rw)
+    proto sub infix:<=:=>(Mu \a, Mu \b) returns Bool:D is assoc<chain>
+    multi sub infix:<=:=>(Mu \a, Mu \b)
 
 Container identity. Returns L<True> if both arguments are bound to the same
-container.
+container. If it returns C<True>, it generally means that modifying one will
+also modify the other.
+
+    my ($a, $b) = (1, 3);
+    say $a =:= $b;      # False
+    $b = 2;
+    say $a;             # 1
+    $b := $a;
+    say $a =:= $b;      # True
+    $a = 5;
+    say $b;             # 5
 
 =head2 infix C«~~»