thtub httub tthub tthub httub thtub thutb htutb tuhtb uthtb huttb uhttb ttuhb ttuhb tuthb utthb tuthb utthb htutb thutb huttb uhttb tuhtb uthtb thtbu httbu tthbu tthbu httbu thtbu thbtu htbtu tbhtu bthtu hbttu bhttu ttbhu ttbhu tbthu btthu tbthu btthu htbtu thbtu hbttu bhttu tbhtu bthtu thubt htubt tuhbt uthbt hutbt uhtbt thbut htbut tbhut bthut hbtut bhtut tubht utbht tbuht btuht ubtht butht hubtt uhbtt hbutt bhutt ubhtt buhtt ttubh ttubh tutbh uttbh tutbh uttbh ttbuh ttbuh tbtuh bttuh tbtuh bttuh tubth utbth tbuth btuth ubtth butth tubth utbth tbuth btuth ubtth butth htubt thubt hutbt uhtbt tuhbt uthbt htbut thbut hbtut bhtut tbhut bthut hubtt uhbtt hbutt bhutt ubhtt buhtt tubht utbht tbuht btuht ubtht butht
Note: these 'words' (valid or invalid) are all the permutations of the word thtub. These words are obtained by scrambling the letters in thtub.