def control(key):
    """Make a string that tmux will parse as the control key (:kbd:`Ctrl`) and
    ``key`` pressed at the same time.

    .. note::

       The ``key`` parameter is case-sensitive. If ``key`` is uppercase, it's
       equivalent to entering :kbd:`Shift` and the key.

       .. doctest::

          >>> from oraide.keys import control
          >>> control('a')  # ctrl + a
          'C-a'
          >>> control('A')  # ctrl + shift + a
          'C-A'
       """
    return 'C-{}'.format(key)
