recur ercur rceur creur ecrur cerur reucr erucr ruecr urecr eurcr uercr rcuer cruer rucer urcer curer ucrer ecurr ceurr eucrr uecrr cuerr ucerr recru ercru rceru creru ecrru cerru rercu errcu rrecu rrecu errcu rercu rcreu crreu rrceu rrceu crreu rcreu ecrru cerru ercru recru creru rceru reurc erurc ruerc urerc eurrc uerrc reruc erruc rreuc rreuc erruc reruc rurec urrec rruec rruec urrec rurec eurrc uerrc erurc reurc urerc ruerc rcure crure rucre urcre curre ucrre rcrue crrue rrcue rrcue crrue rcrue rurce urrce rruce rruce urrce rurce curre ucrre crure rcure urcre rucre ecurr ceurr eucrr uecrr cuerr ucerr ecrur cerur ercur recur creur rceur eurcr uercr erucr reucr urecr ruecr curer ucrer cruer rcuer urcer rucer
Note: these 'words' (valid or invalid) are all the permutations of the word recur. These words are obtained by scrambling the letters in recur.