> [tr] won't work as expected 

Hmm, I see.  

> you would still lose the idea of tabs as . . . 
> "jump to the next tab stop".  
> expand will take care of this.  

Aha!  Now I understand why expand was necessary 
to provide this additional functionality over 
and above the capability of tr and sed.  

Thanks.  This is very helpful.  

Kindest regards,

Tom