[CMake] include problems

[Lode Leroy]

I have a something.cmake file that works when included directly, but
does not work when it is included from inside a function.

can someone explain if there is an intentional difference, and what it
is, between

                include(something)

and

                function(use_something)
                         include(something)
                endfunction()
                use_something()

in other words: how can I make the function use_something() behave as
include(something)?