refcu erfcu rfecu frecu efrcu fercu recfu ercfu rcefu crefu ecrfu cerfu rfceu frceu rcfeu crfeu fcreu cfreu efcru fecru ecfru cefru fceru cferu refuc erfuc rfeuc freuc efruc feruc reufc erufc ruefc urefc eurfc uerfc rfuec fruec rufec urfec furec ufrec efurc feurc eufrc uefrc fuerc uferc recuf ercuf rceuf creuf ecruf ceruf reucf erucf ruecf urecf eurcf uercf rcuef cruef rucef urcef curef ucref ecurf ceurf eucrf uecrf cuerf ucerf rfcue frcue rcfue crfue fcrue cfrue rfuce fruce rufce urfce furce ufrce rcufe crufe rucfe urcfe curfe ucrfe fcure cfure fucre ufcre cufre ucfre efcur fecur ecfur cefur fceur cfeur efucr feucr eufcr uefcr fuecr ufecr ecufr ceufr eucfr uecfr cuefr ucefr fcuer cfuer fucer ufcer cufer ucfer
Note: these 'words' (valid or invalid) are all the permutations of the word refcu. These words are obtained by scrambling the letters in refcu.