fribs rfibs firbs ifrbs rifbs irfbs frbis rfbis fbris bfris rbfis brfis fibrs ifbrs fbirs bfirs ibfrs bifrs ribfs irbfs rbifs brifs ibrfs birfs frisb rfisb firsb ifrsb rifsb irfsb frsib rfsib fsrib sfrib rsfib srfib fisrb ifsrb fsirb sfirb isfrb sifrb risfb irsfb rsifb srifb isrfb sirfb frbsi rfbsi fbrsi bfrsi rbfsi brfsi frsbi rfsbi fsrbi sfrbi rsfbi srfbi fbsri bfsri fsbri sfbri bsfri sbfri rbsfi brsfi rsbfi srbfi bsrfi sbrfi fibsr ifbsr fbisr bfisr ibfsr bifsr fisbr ifsbr fsibr sfibr isfbr sifbr fbsir bfsir fsbir sfbir bsfir sbfir ibsfr bisfr isbfr sibfr bsifr sbifr ribsf irbsf rbisf brisf ibrsf birsf risbf irsbf rsibf sribf isrbf sirbf rbsif brsif rsbif srbif bsrif sbrif ibsrf bisrf isbrf sibrf bsirf sbirf
Note: these 'words' (valid or invalid) are all the permutations of the word fribs. These words are obtained by scrambling the letters in fribs.