pretw rpetw pertw eprtw reptw erptw prtew rptew ptrew tprew rtpew trpew petrw eptrw pterw tperw etprw teprw retpw ertpw rtepw trepw etrpw terpw prewt rpewt perwt eprwt repwt erpwt prwet rpwet pwret wpret rwpet wrpet pewrt epwrt pwert wpert ewprt weprt rewpt erwpt rwept wrept ewrpt werpt prtwe rptwe ptrwe tprwe rtpwe trpwe prwte rpwte pwrte wprte rwpte wrpte ptwre tpwre pwtre wptre twpre wtpre rtwpe trwpe rwtpe wrtpe twrpe wtrpe petwr eptwr ptewr tpewr etpwr tepwr pewtr epwtr pwetr wpetr ewptr weptr ptwer tpwer pwter wpter twper wtper etwpr tewpr ewtpr wetpr twepr wtepr retwp ertwp rtewp trewp etrwp terwp rewtp erwtp rwetp wretp ewrtp wertp rtwep trwep rwtep wrtep twrep wtrep etwrp tewrp ewtrp wetrp twerp wterp
Note: these 'words' (valid or invalid) are all the permutations of the word pretw. These words are obtained by scrambling the letters in pretw.