treif rteif terif etrif retif ertif trief rtief tiref itref ritef irtef teirf etirf tierf iterf eitrf ietrf reitf eritf rietf iretf eirtf iertf trefi rtefi terfi etrfi retfi ertfi trfei rtfei tfrei ftrei rftei frtei tefri etfri tferi fteri eftri fetri refti erfti rfeti freti efrti ferti trife rtife tirfe itrfe ritfe irtfe trfie rtfie tfrie ftrie rftie frtie tifre itfre tfire ftire iftre fitre rifte irfte rfite frite ifrte firte teifr etifr tiefr itefr eitfr ietfr tefir etfir tfeir fteir eftir fetir tifer itfer tfier ftier ifter fiter eiftr ieftr efitr feitr ifetr fietr reift erift rieft ireft eirft ierft refit erfit rfeit freit efrit ferit rifet irfet rfiet friet ifret firet eifrt iefrt efirt feirt ifert fiert
Note: these 'words' (valid or invalid) are all the permutations of the word treif. These words are obtained by scrambling the letters in treif.