rtube trube rutbe urtbe turbe utrbe rtbue trbue rbtue brtue tbrue btrue rubte urbte rbute brute ubrte burte tubre utbre tbure bture ubtre butre rtueb trueb ruteb urteb tureb utreb rteub treub retub ertub terub etrub ruetb uretb reutb erutb uertb eurtb tuerb uterb teurb eturb uetrb eutrb rtbeu trbeu rbteu brteu tbreu btreu rtebu trebu retbu ertbu terbu etrbu rbetu bretu rebtu erbtu bertu ebrtu tberu bteru tebru etbru betru ebtru rubet urbet rbuet bruet ubret buret ruebt urebt reubt erubt uerbt eurbt rbeut breut rebut erbut berut ebrut ubert buert uebrt eubrt beurt eburt tuber utber tbuer btuer ubter buter tuebr utebr teubr etubr uetbr eutbr tbeur bteur tebur etbur betur ebtur ubetr buetr uebtr eubtr beutr ebutr
Note: these 'words' (valid or invalid) are all the permutations of the word rtube. These words are obtained by scrambling the letters in rtube.