slack lsack salck aslck lasck alsck slcak lscak sclak cslak lcsak clsak saclk asclk scalk csalk acslk caslk lacsk alcsk lcask clask aclsk calsk slakc lsakc salkc aslkc laskc alskc slkac lskac sklac kslac lksac klsac saklc asklc skalc ksalc akslc kaslc laksc alksc lkasc klasc aklsc kalsc slcka lscka sclka cslka lcska clska slkca lskca sklca kslca lksca klsca sckla cskla skcla kscla cksla kcsla lcksa clksa lkcsa klcsa cklsa kclsa sackl asckl scakl csakl acskl caskl sakcl askcl skacl ksacl akscl kascl sckal cskal skcal kscal cksal kcsal acksl caksl akcsl kacsl ckasl kcasl lacks alcks lcaks claks aclks calks lakcs alkcs lkacs klacs aklcs kalcs lckas clkas lkcas klcas cklas kclas ackls cakls akcls kacls ckals kcals
Note: these 'words' (valid or invalid) are all the permutations of the word slack. These words are obtained by scrambling the letters in slack.