Hi nick, below code will throw error on verify:
Keyboard.press(KEY_PRNT_SCRN); //Yet Did not find modifier key for Print screen.
delay(100);
Keyboard.releaseAll();
it throws compile error as "error: 'KEY_PRNT_SCRN' was not declared in this scope"
As KEY_PRNT_SCRN is not supported modifier key available in list:
http://arduino.cc/en/Reference/KeyboardModifiers