sets the back search flag. When this flag is true, every search or replacement command is performed backwards.
If you invoke
SearchBack with no arguments, it will toggle the flag. If you
specify 0 or 1, the flag will be set to false or true, respectively. A lower
case ‘b’ will appear on the status bar if the flag is true.
Note that this flag also can be set through interactions with the
Replace command. See Replace.