prukc rpukc purkc uprkc rupkc urpkc prkuc rpkuc pkruc kpruc rkpuc krpuc pukrc upkrc pkurc kpurc ukprc kuprc rukpc urkpc rkupc krupc ukrpc kurpc pruck rpuck purck uprck rupck urpck prcuk rpcuk pcruk cpruk rcpuk crpuk pucrk upcrk pcurk cpurk ucprk cuprk rucpk urcpk rcupk crupk ucrpk curpk prkcu rpkcu pkrcu kprcu rkpcu krpcu prcku rpcku pcrku cprku rcpku crpku pkcru kpcru pckru cpkru kcpru ckpru rkcpu krcpu rckpu crkpu kcrpu ckrpu pukcr upkcr pkucr kpucr ukpcr kupcr puckr upckr pcukr cpukr ucpkr cupkr pkcur kpcur pckur cpkur kcpur ckpur ukcpr kucpr uckpr cukpr kcupr ckupr rukcp urkcp rkucp krucp ukrcp kurcp ruckp urckp rcukp crukp ucrkp curkp rkcup krcup rckup crkup kcrup ckrup ukcrp kucrp uckrp cukrp kcurp ckurp
Note: these 'words' (valid or invalid) are all the permutations of the word prukc. These words are obtained by scrambling the letters in prukc.