prief rpief piref ipref ripef irpef preif rpeif perif eprif repif erpif pierf iperf peirf epirf ieprf eiprf riepf irepf reipf eripf ierpf eirpf prife rpife pirfe iprfe ripfe irpfe prfie rpfie pfrie fprie rfpie frpie pifre ipfre pfire fpire ifpre fipre rifpe irfpe rfipe fripe ifrpe firpe prefi rpefi perfi eprfi repfi erpfi prfei rpfei pfrei fprei rfpei frpei pefri epfri pferi fperi efpri fepri refpi erfpi rfepi frepi efrpi ferpi piefr ipefr peifr epifr iepfr eipfr pifer ipfer pfier fpier ifper fiper pefir epfir pfeir fpeir efpir fepir iefpr eifpr ifepr fiepr efipr feipr riefp irefp reifp erifp ierfp eirfp rifep irfep rfiep friep ifrep firep refip erfip rfeip freip efrip ferip iefrp eifrp iferp fierp efirp feirp
Note: these 'words' (valid or invalid) are all the permutations of the word prief. These words are obtained by scrambling the letters in prief.