hatrf ahtrf htarf tharf athrf tahrf hartf ahrtf hratf rhatf arhtf rahtf htraf thraf hrtaf rhtaf trhaf rthaf atrhf tarhf arthf rathf trahf rtahf hatfr ahtfr htafr thafr athfr tahfr haftr ahftr hfatr fhatr afhtr fahtr htfar thfar hftar fhtar tfhar fthar atfhr tafhr afthr fathr tfahr ftahr harft ahrft hraft rhaft arhft rahft hafrt ahfrt hfart fhart afhrt fahrt hrfat rhfat hfrat fhrat rfhat frhat arfht rafht afrht farht rfaht fraht htrfa thrfa hrtfa rhtfa trhfa rthfa htfra thfra hftra fhtra tfhra fthra hrfta rhfta hfrta fhrta rfhta frhta trfha rtfha tfrha ftrha rftha frtha atrfh tarfh artfh ratfh trafh rtafh atfrh tafrh aftrh fatrh tfarh ftarh arfth rafth afrth farth rfath frath trfah rtfah tfrah ftrah rftah frtah
Note: these 'words' (valid or invalid) are all the permutations of the word hatrf. These words are obtained by scrambling the letters in hatrf.