reifs erifs riefs irefs eirfs ierfs refis erfis rfeis freis efris feris rifes irfes rfies fries ifres fires eifrs iefrs efirs feirs ifers fiers reisf erisf riesf iresf eirsf iersf resif ersif rseif sreif esrif serif risef irsef rsief srief isref siref eisrf iesrf esirf seirf iserf sierf refsi erfsi rfesi fresi efrsi fersi resfi ersfi rsefi srefi esrfi serfi rfsei frsei rsfei srfei fsrei sfrei efsri fesri esfri sefri fseri sferi rifse irfse rfise frise ifrse firse risfe irsfe rsife srife isrfe sirfe rfsie frsie rsfie srfie fsrie sfrie ifsre fisre isfre sifre fsire sfire eifsr iefsr efisr feisr ifesr fiesr eisfr iesfr esifr seifr isefr siefr efsir fesir esfir sefir fseir sfeir ifser fiser isfer sifer fsier sfier
Note: these 'words' (valid or invalid) are all the permutations of the word reifs. These words are obtained by scrambling the letters in reifs.