However, in doing so I have run into a snag which I previously skipped over and ignored: I don't actually know what the @variable@ syntax means/does, or what parses it. It's not Makefile syntax, as far as I've been able to determine. I haven't thus far found any documentation for debian/control.in at all; my searches are leading me only to documentation for debian/control, which doesn't mention any .in file as far as I've found.
If it's not Makefile, it's quite possibly cmake based which in
turn can generate dynamic makefiles at various stages in the
build.
The downside is that cmake for large projects has nuances that require years of direct cmake experience to fully understand what is going on.
Search for some CMakeFiles.txt files to check if you need to
explore cmake further.
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