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