fasts afsts fsats sfats asfts safts fatss aftss ftass tfass atfss tafss fstas sftas ftsas tfsas stfas tsfas astfs satfs atsfs tasfs stafs tsafs fasst afsst fsast sfast asfst safst fasst afsst fsast sfast asfst safst fssat sfsat fssat sfsat ssfat ssfat assft sasft assft sasft ssaft ssaft fatss aftss ftass tfass atfss tafss fasts afsts fsats sfats asfts safts ftsas tfsas fstas sftas tsfas stfas atsfs tasfs astfs satfs tsafs stafs fstsa sftsa ftssa tfssa stfsa tsfsa fssta sfsta fssta sfsta ssfta ssfta ftssa tfssa fstsa sftsa tsfsa stfsa stsfa tssfa sstfa sstfa tssfa stsfa astsf satsf atssf tassf stasf tsasf asstf sastf asstf sastf ssatf ssatf atssf tassf astsf satsf tsasf stasf stsaf tssaf sstaf sstaf tssaf stsaf
Note: these 'words' (valid or invalid) are all the permutations of the word fasts. These words are obtained by scrambling the letters in fasts.