tills itlls tlils ltils iltls litls tills itlls tlils ltils iltls litls tllis ltlis tllis ltlis lltis lltis illts lilts illts lilts llits llits tilsl itlsl tlisl ltisl iltsl litsl tisll itsll tsill still istll sitll tlsil ltsil tslil stlil lstil sltil ilstl listl isltl siltl lsitl slitl tilsl itlsl tlisl ltisl iltsl litsl tisll itsll tsill still istll sitll tlsil ltsil tslil stlil lstil sltil ilstl listl isltl siltl lsitl slitl tllsi ltlsi tllsi ltlsi lltsi lltsi tlsli ltsli tslli stlli lstli sltli tlsli ltsli tslli stlli lstli sltli llsti llsti lslti sllti lslti sllti illst lilst illst lilst llist llist ilslt lislt isllt sillt lsilt slilt ilslt lislt isllt sillt lsilt slilt llsit llsit lslit sllit lslit sllit
Note: these 'words' (valid or invalid) are all the permutations of the word tills. These words are obtained by scrambling the letters in tills.