def  next_regex str
      first = nil
      ## content can be string or Chunkline, so we had to write <tt>index</tt> for this.
      ## =~ does not give an error, but it does not work.
      @list.each_with_index do |line, ix|
        col = line =~ /#{str}/
        if col
          first ||= [ ix, col ]
          if ix > @current_index
            return [ix, col]
          end
        end
      end
      return first
    end
def  next_regex str
      first = nil
      ## content can be string or Chunkline, so we had to write <tt>index</tt> for this.
      ## =~ does not give an error, but it does not work.
      @list.each_with_index do |line, ix|
        col = line =~ /#{str}/
        if col
          first ||= [ ix, col ]
          if ix > @current_index
            return [ix, col]
          end
        end
      end
      return first
    end
Find the next row that contains given string
 @return row and col offset of match, or nil
 @param String to find