I have a text file *temp.txt* containing 

```none
Hello World
My name is MayukhSarkar
My name is mayukh
My name is MAYUKH
My name is MaYuKh
My name is mAyUkH

```

The sed command

```
sed 's/\b[M,m][A,a][Y,y][U,u][K,k][H,h]\b/sobo/g' temp.txt

```

is not replacing the occurrences of `Mayukh` with `sobo`

but the sed command without `\b` is working

```
sed 's/[M,m][A,a][Y,y][U,u][K,k][H,h]/sobo/g' temp.txt

```

but it is also replacing the `MayukhSarkar` into `soboSarkar`