sed -i -E "s/еж([аиу][^а-я])/ёжик\1/g" *ru*
grep -E "еж[аиу][^а-я]" *ru*
Comment: [^а-я] includes all spaces and punctuation and also finish of string
AAAAtHicFc6xDsFQHIXxc3tv+48oHUw2kRKv4Am8hYjFC4hGYjuLwWRi6+QVDDazxGbpYpHYPEL1LL9845cVVsD9/BrdjR/Cju4Cv6oHSM8Ndk32sDL0gYVVzN5WQahyZJXlRNlUdIq/FLBb/KJAp44fFAjTcKBAMvFbCrR2fkmBdBbmFAgWjSngnm5EgfY96lE0f/hQ4A+Rki/Q