Why doesn't i<Ctrl-R>=expandcmd('se shm') work?

Question

I'm trying to do i<Ctrl-R>=expandcmd('se shm') and more generally i<Ctrl-R>=expandcmd({expr}) but I'm just getting the literal {expr} inserted.

When I type :se shm<CR> I get the value of the option printed on the command-line. I'd like that inserted into my buffer.

Answer 1

expandcmd() expands wildcards, environment variables and such. It is not intended for VimScript execution.

In general, you can use execute() function to run VimScript interpreter and get the ouput as a string. But in this case it's enough to use &-notation (see :h expr-option):

i<C-R>=&shm