It isn't at all too late in the development process. Here's a quote:
[[
Why the tab in column 1? Yacc was new, Lex was brand new. I hadn't
tried either, so I figured this would be a good excuse to learn. After
getting myself snarled up with my first stab at Lex, I just did
something simple with the pattern newline-tab. It worked, it stayed.
And then a few weeks later I had a user population of about a dozen,
most of them friends, and I didn't want to screw up my embedded base.
The rest, sadly, is history.
- Stu Feldman, author of make
]]