preop rpeop perop eprop repop erpop proep rpoep porep oprep ropep orpep peorp eporp poerp operp eoprp oeprp reopp eropp roepp orepp eorpp oerpp prepo rpepo perpo eprpo reppo erppo prpeo rppeo ppreo ppreo rppeo prpeo pepro eppro ppero ppero eppro pepro reppo erppo rpepo prepo eprpo perpo prope rpope porpe oprpe roppe orppe prpoe rppoe pproe pproe rppoe prpoe popre oppre ppore ppore oppre popre roppe orppe rpope prope oprpe porpe peopr epopr poepr opepr eoppr oeppr pepor eppor ppeor ppeor eppor pepor poper opper ppoer ppoer opper poper eoppr oeppr epopr peopr opepr poepr reopp eropp roepp orepp eorpp oerpp repop erpop rpeop preop eprop perop ropep orpep rpoep proep oprep porep eoprp oeprp eporp peorp operp poerp
Note: these 'words' (valid or invalid) are all the permutations of the word preop. These words are obtained by scrambling the letters in preop.