trfg rtfg tfrg ftrg rftg frtg trgf rtgf tgrf gtrf rgtf grtf tfgr ftgr tgfr gtfr fgtr gftr rfgt frgt rgft grft fgrt gfrt
Note: these 'words' (valid or invalid) are all the permutations of the word trfg. These words are obtained by scrambling the letters in trfg.