grex rgex gerx egrx regx ergx grxe rgxe gxre xgre rxge xrge gexr egxr gxer xger exgr xegr rexg erxg rxeg xreg exrg xerg
Note: these 'words' (valid or invalid) are all the permutations of the word grex. These words are obtained by scrambling the letters in grex.