lefts elfts lfets flets eflts felts letfs eltfs ltefs tlefs etlfs telfs lftes fltes ltfes tlfes ftles tfles eftls fetls etfls tefls ftels tfels lefst elfst lfest flest eflst felst lesft elsft lseft sleft eslft selft lfset flset lsfet slfet fslet sflet efslt feslt esflt seflt fselt sfelt letsf eltsf ltesf tlesf etlsf telsf lestf elstf lsetf sletf esltf seltf ltsef tlsef lstef sltef tslef stlef etslf teslf estlf setlf tself stelf lftse fltse ltfse tlfse ftlse tflse lfste flste lsfte slfte fslte sflte ltsfe tlsfe lstfe sltfe tslfe stlfe ftsle tfsle fstle sftle tsfle stfle eftsl fetsl etfsl tefsl ftesl tfesl efstl festl esftl seftl fsetl sfetl etsfl tesfl estfl setfl tsefl stefl ftsel tfsel fstel sftel tsfel stfel
Note: these 'words' (valid or invalid) are all the permutations of the word lefts. These words are obtained by scrambling the letters in lefts.