read_escape

# File lib/irb/ruby-lex.rb, line 1101
  def read_escape
    case ch = getc
    when "\n", "\r", "\f"
    when "\\", "n", "t", "r", "f", "v", "a", "e", "b", "s" #"
    when /[0-7]/
      ungetc ch
      3.times do
        case ch = getc
        when /[0-7]/
        when nil
          break
        else
          ungetc
          break
        end
      end
      
    when "x"
      2.times do
        case ch = getc
        when /[0-9a-fA-F]/
        when nil
          break
        else
          ungetc
          break
        end
      end

    when "M"
      if (ch = getc) != '-'
        ungetc
      else
        if (ch = getc) == "\\" #"
          read_escape
        end
      end

    when "C", "c" #, "^"
      if ch == "C" and (ch = getc) != "-"
        ungetc
      elsif (ch = getc) == "\\" #"
        read_escape
      end
    else
      # other characters 
    end
  end