first ifrst frist rfist irfst rifst fisrt ifsrt fsirt sfirt isfrt sifrt frsit rfsit fsrit sfrit rsfit srfit irsft risft isrft sirft rsift srift firts ifrts frits rfits irfts rifts fitrs iftrs ftirs tfirs itfrs tifrs frtis rftis ftris tfris rtfis trfis irtfs ritfs itrfs tirfs rtifs trifs fistr ifstr fsitr sfitr isftr siftr fitsr iftsr ftisr tfisr itfsr tifsr fstir sftir ftsir tfsir stfir tsfir istfr sitfr itsfr tisfr stifr tsifr frsti rfsti fsrti sfrti rsfti srfti frtsi rftsi ftrsi tfrsi rtfsi trfsi fstri sftri ftsri tfsri stfri tsfri rstfi srtfi rtsfi trsfi strfi tsrfi irstf ristf isrtf sirtf rsitf sritf irtsf ritsf itrsf tirsf rtisf trisf istrf sitrf itsrf tisrf stirf tsirf rstif srtif rtsif trsif strif tsrif
Note: these 'words' (valid or invalid) are all the permutations of the word first. These words are obtained by scrambling the letters in first.