def add!(char)
      left, cursor, right = abbrev_segments
      @abbrev = left + char + cursor + right
      @col += 1
      redraw
    end
def add!(char)
      left, cursor, right = abbrev_segments
      @abbrev = left + char + cursor + right
      @col += 1
      redraw
    end
Insert a character at (before) the current cursor position.