Intro/Tag 0:00-0:05 C Major
Verse 1 0:05-0:34 C Major
Tag 0:34-0:38 C Major
Verse 2 0:38-1:14 C Major
Tag 1:07-1:14 transitional (C Major to A Major)
Middle 8 1:14-1:42 A Major
Solo (v) 1:42-2:10 C Major
Tag 2:10-2:14 C Major
Verse 3 2:14-2:43 C Major
Coda/Tag x2 2:43-3:02 C Major (A Major)*
Comments: The tag's structural function is textbook, serving as both the intro and outro, plus serving as "structural glue" to adhere the various formal components together into a composite whole, and also helping articulate the large-scale tonal design of the song through transitional passages.
In addition to all of that, the range of the opening tag (a to c) anticipates the macro-scale tonal plan of A major juxtaposed with C major, something the Beatles had done previously in  "Another Girl",  "You're Going to Lose That Girl",  "Lady Madonna",  "Birthday", and  "The Continuing Story of Bungalow Bill", and would use extensively on the B-side of Abbey Road.