perst eprst prest rpest erpst repst pesrt epsrt psert spert esprt seprt prset rpset psret spret rspet srpet erspt respt esrpt serpt rsept srept perts eprts prets rpets erpts repts petrs eptrs pters tpers etprs teprs prtes rptes ptres tpres rtpes trpes ertps retps etrps terps rteps treps pestr epstr psetr spetr esptr septr petsr eptsr ptesr tpesr etpsr tepsr pster spter ptser tpser stper tsper estpr setpr etspr tespr stepr tsepr prste rpste psrte sprte rspte srpte prtse rptse ptrse tprse rtpse trpse pstre sptre ptsre tpsre stpre tspre rstpe srtpe rtspe trspe strpe tsrpe erstp restp esrtp sertp rsetp sretp ertsp retsp etrsp tersp rtesp tresp estrp setrp etsrp tesrp sterp tserp rstep srtep rtsep trsep strep tsrep
Note: these 'words' (valid or invalid) are all the permutations of the word perst. These words are obtained by scrambling the letters in perst.