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
AAABkHicFdCxK8RhGAfw7/u87/v8zns/9y63Wij+A5SE8YYbXErCplgMRBxXBgveS91goOQGN1jdImVw0xlOucGVQcpgk9hQ/J7l07fn21NPj9vGtIoW+Ej5Ne5WVtsVpcfsgPITKCo/qmrK5+hemV7eqgtwbd6rC6AWl0/iVS7D9PPOmwD3yHuvAqjElXZ3D1eQrFWCIO1xEKR1gTbxCSG47ySZyK4GE+kmhBA/S0rTlMwewAWaCVzQF0itJ7NUMUmuRPPBlfQ54mvbaMbX0SnUix1/oFZ0Bc7bnaqA1KLZqApwLTt0JsAvoavul7SG/9JPZf8V/SLj6K7jR+gOmVlV6/hBVUNmGcWOH0MR6Qjv++no71ZuqX0IcsHFhwDOqb7AOSrBHSTJHdIl6EYVGnRjf2DyqtkweT2X/E8NN1ybHmGYJoNhu4k4S9ldAf9Gt2jZ