REDO
    The Redo Command enables users to capture the previously typed
DCL command for editing.  This feature is especially useful when
typos are made in long command strings.  The user need only correct
the typos rather than retype the whole command string. 

    The user must first enable the Redo Command Line Interpreter by
typing $REDOCLI to allow the use of the Redo command. This command
line interpreter is virtually transparent to the user and captures
the previous DCL command for Redo to act upon. To disable the Redo
Command Line Interpreter, type \\ .