refer erfer rfeer freer efrer ferer reefr erefr reefr erefr eerfr eerfr rfeer freer refer erfer ferer efrer eferr feerr eefrr eefrr feerr eferr refre erfre rfere frere efrre ferre rerfe errfe rrefe rrefe errfe rerfe rfree frree rrfee rrfee frree rfree efrre ferre erfre refre frere rfere reerf ererf reerf ererf eerrf eerrf reref erref rreef rreef erref reref reref erref rreef rreef erref reref eerrf eerrf ererf reerf ererf reerf rfere frere refre erfre ferre efrre rfree frree rrfee rrfee frree rfree rerfe errfe rrefe rrefe errfe rerfe ferre efrre frere rfere erfre refre eferr feerr eefrr eefrr feerr eferr efrer ferer erfer refer freer rfeer eerfr eerfr erefr reefr erefr reefr ferer efrer freer rfeer erfer refer
Note: these 'words' (valid or invalid) are all the permutations of the word refer. These words are obtained by scrambling the letters in refer.