hifst ihfst hfist fhist ifhst fihst hisft ihsft hsift shift ishft sihft hfsit fhsit hsfit shfit fshit sfhit ifsht fisht isfht sifht fsiht sfiht hifts ihfts hfits fhits ifhts fihts hitfs ihtfs htifs thifs ithfs tihfs hftis fhtis htfis thfis fthis tfhis ifths fiths itfhs tifhs ftihs tfihs histf ihstf hsitf shitf ishtf sihtf hitsf ihtsf htisf thisf ithsf tihsf hstif shtif htsif thsif sthif tshif isthf sithf itshf tishf stihf tsihf hfsti fhsti hsfti shfti fshti sfhti hftsi fhtsi htfsi thfsi fthsi tfhsi hstfi shtfi htsfi thsfi sthfi tshfi fsthi sfthi ftshi tfshi stfhi tsfhi ifsth fisth isfth sifth fsith sfith iftsh fitsh itfsh tifsh ftish tfish istfh sitfh itsfh tisfh stifh tsifh fstih sftih ftsih tfsih stfih tsfih
Note: these 'words' (valid or invalid) are all the permutations of the word hifst. These words are obtained by scrambling the letters in hifst.