It's been a long time, but here's how the rule works (rot13.com): guerr-va-n-ebj bayl pbhagf jura gur fgngrf bs guerr pbafrphgvir gvyrf ner PBZCYRGRYL gur fnzr. Sbe rknzcyr, bar gvyr bayl unf n obk, nabgure gvyr unf n obk naq n gnetrg, gura gurfr gjb qbrf ABG unir gur fnzr fgngr.