bilk iblk blik lbik ilbk libk bikl ibkl bkil kbil ikbl kibl blki lbki bkli kbli lkbi klbi ilkb likb iklb kilb lkib klib
Note: these 'words' (valid or invalid) are all the permutations of the word bilk. These words are obtained by scrambling the letters in bilk.