pyperclip(Python package)xsel(system package/program/utility)
Put the sequence of messages in ~/.clipboard. Use cbm.py to iterate over the messages (and update clipboard) if the current clipboard is one of them. Use cbm.py -b to iterate backward (and update clipboard).
By default, the messages are separated by \n\n\n to support multi-line message in clipboard.
You can customize CLIPBOARD_QUEUE_FILE and/or CLIPBOARD_SEPARATOR in cbm.py.