def backspace!
      if @col > 0
        left, cursor, right = abbrev_segments
        @abbrev = left.chop! + cursor + right
        @col -= 1
        redraw
      end
    end
def backspace!
      if @col > 0
        left, cursor, right = abbrev_segments
        @abbrev = left.chop! + cursor + right
        @col -= 1
        redraw
      end
    end
Delete a character to the left of the current cursor position.