rifer irfer rfier frier ifrer firer riefr irefr reifr erifr ierfr eirfr rfeir freir refir erfir ferir efrir iferr fierr iefrr eifrr feirr efirr rifre irfre rfire frire ifrre firre rirfe irrfe rrife rrife irrfe rirfe rfrie frrie rrfie rrfie frrie rfrie ifrre firre irfre rifre frire rfire rierf irerf reirf erirf ierrf eirrf riref irref rrief rrief irref riref rerif errif rreif rreif errif rerif ierrf eirrf irerf rierf erirf reirf rferi freri refri erfri ferri efrri rfrei frrei rrfei rrfei frrei rfrei rerfi errfi rrefi rrefi errfi rerfi ferri efrri freri rferi erfri refri iferr fierr iefrr eifrr feirr efirr ifrer firer irfer rifer frier rfier ierfr eirfr irefr riefr erifr reifr ferir efrir freir rfeir erfir refir
Note: these 'words' (valid or invalid) are all the permutations of the word rifer. These words are obtained by scrambling the letters in rifer.