It's in the V7 sources and binaries in the TUHS archives: 

% find . -name '*struct*' -print
./bin/struct
./usr/lib/struct
./usr/lib/struct/structure
./usr/man/man1/struct.1
./usr/src/cmd/struct


On Sat, Mar 14, 2020 at 7:31 AM Harald Arnesen <skogtun@gmail.com> wrote:
Doug McIlroy [14.03.2020 00:31]:

> struct
>
> Brenda Baker undertook her Fortan-to-Ratfor converter against the advice
> of her department head--me. I thought it would likely produce an ad hoc
> reordering of the orginal, freed of statement numbers, but otherwise no
> more readable than a properly indented Fortran program. Brenda proved
> me wrong. She discovered that every Fortran program has a canonically
> structured form. Programmers preferred the canonicalized form to what
> they had originally written.

I've been trying to find the source to this. I have lots of old
spaghetti-Fortran routines from a former job, and I would love to try
making it somewhat understandable.
--
Hilsen Harald