What's so hard with doing s/\t/g / or s/ /\t/g?
I use 8-space tabs, so what? It is a single character, \t and the way it is represented is system dependant.
If i have, say 1000 tabs in my source code it's 1000 bytes; If i'd use 4 spaces it would be 4000 bytes, which is a horrible waste of bytes.
And 1000 tabs are not many, a src of 1000 lines should have at least 1000 tabs.