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