Document new opcode.

Author: markshannon

Doc/library/dis.rst

@@ -991,6 +991,15 @@ All of the following opcodes use their arguments.
       ``i`` is no longer offset by the length of ``co_varnames``.
 
 
+.. opcode:: COPY_FREE_VARS (n)
+
+   Copies the ``n`` free variables from the closure into the frame.
+   Removes the need for special code on the caller's side when calling
+   closures.
+
+   .. versionadded:: 3.11
+
+
 .. opcode:: RAISE_VARARGS (argc)
 
    Raises an exception using one of the 3 forms of the ``raise`` statement,