This file will go through autoconf variable substitution.

The output file will be named as 'test-output.txt' (the '.in'-suffix
is stripped).

All names surrounded by '@'-characters will be replaced by the values
of the variables (if present) by the configure script when it is run
by end user.

Prefix: @prefix@
C compiler: @CC@

This is a name for which there is no variable.
Stuff: @stuff@