I've seen various topics on how to iterate through multiple file extensions but in most case, the list is defined.

example: 

```
for file in ${arg}/**/*.{txt,h,py}
do
    ....
done

```

As can be seen, `.TXT` files would be ignored. And sadly, the guy who answered it says it only works for bash4. but my setup uses bash3.x.

Any ideas on how it can be done?