right-alt

daniel@timecube:~/misc$ p right.txt
kb mode was UNICODE
[ if you are trying this under X, it might not work
since the X server is also reading /dev/console ]

press any key (program terminates 10s after last keypress)...
keycode  28 release # Enter key
keycode 100 press   # Right alt
keycode  42 press   # Left shift
keycode  42 press
keycode  43 press   # Backslash key
keycode  43 press
keycode  43 press
keycode  43 press
keycode  43 press
keycode  43 press
keycode  43 press
keycode  43 press
keycode 100 release
keycode  42 release
keycode  43 release