stapk tsapk satpk astpk taspk atspk stpak tspak sptak pstak tpsak ptsak saptk asptk spatk psatk apstk pastk tapsk atpsk tpask ptask aptsk patsk stakp tsakp satkp astkp taskp atskp stkap tskap sktap kstap tksap ktsap saktp asktp skatp ksatp akstp kastp taksp atksp tkasp ktasp aktsp katsp stpka tspka sptka pstka tpska ptska stkpa tskpa sktpa kstpa tkspa ktspa spkta pskta skpta kspta pksta kpsta tpksa ptksa tkpsa ktpsa pktsa kptsa sapkt aspkt spakt psakt apskt paskt sakpt askpt skapt ksapt akspt kaspt spkat pskat skpat kspat pksat kpsat apkst pakst akpst kapst pkast kpast tapks atpks tpaks ptaks aptks patks takps atkps tkaps ktaps aktps katps tpkas ptkas tkpas ktpas pktas kptas apkts pakts akpts kapts pkats kpats
Note: these 'words' (valid or invalid) are all the permutations of the word stapk. These words are obtained by scrambling the letters in stapk.