biwrs ibwrs bwirs wbirs iwbrs wibrs birws ibrws briws rbiws irbws ribws bwris wbris brwis rbwis wrbis rwbis iwrbs wirbs irwbs riwbs wribs rwibs biwsr ibwsr bwisr wbisr iwbsr wibsr biswr ibswr bsiwr sbiwr isbwr sibwr bwsir wbsir bswir sbwir wsbir swbir iwsbr wisbr iswbr siwbr wsibr swibr birsw ibrsw brisw rbisw irbsw ribsw bisrw ibsrw bsirw sbirw isbrw sibrw brsiw rbsiw bsriw sbriw rsbiw srbiw irsbw risbw isrbw sirbw rsibw sribw bwrsi wbrsi brwsi rbwsi wrbsi rwbsi bwsri wbsri bswri sbwri wsbri swbri brswi rbswi bsrwi sbrwi rsbwi srbwi wrsbi rwsbi wsrbi swrbi rswbi srwbi iwrsb wirsb irwsb riwsb wrisb rwisb iwsrb wisrb iswrb siwrb wsirb swirb irswb riswb isrwb sirwb rsiwb sriwb wrsib rwsib wsrib swrib rswib srwib
Note: these 'words' (valid or invalid) are all the permutations of the word biwrs. These words are obtained by scrambling the letters in biwrs.