procedure main()
   write(&error)
   &error := "123"
   write(&error)
   write((x := 3 / "a") | monitor(&line))
   write(&error)
   write(image(x))
   write(&error)
   errorclear()
   write(&errornumber | "no error")
   &error := "a" | monitor(&line)
   write(&error)
end

procedure monitor(line)
   write("error in line ",line,":")
   write("   &error = ",&error)
   write("   &errornumber = ",&errornumber)
   write("   &errortext = ",image(&errortext))
   write("   &errorvalue = ",image(&errorvalue))
   return
end