return <Plug> in a <expr> map

Question

I know that in vim, map <expr> allows us to map a key sequence to a new sequence as specified by the return value of an expression. For example:

function Wrap()
    if getline('.') == ''
        " can I return a <Plug> here?
        return "Ends an empty line\<cr>"
    else
        return "\<cr>"
    endif
endfunction
inoremap <expr> <cr> Wrap()

In the expression, \<cr> means to return the <cr> key.

We can also have <Plug> maps like:

inoremap <Plug>empty "Ends an empty line\<cr>"
imap <cr> <Plug>empty

My question is: if I want to return the <Plug>empty map only when cursor is in an empty line like in the first example, what should I do?

---

As @Mass suggested, the solution is:

inoremap <Plug>empty "Ends an empty line\<cr>"
function Wrap()
    if getline('.') == ''
        return "\<Plug>empty"
    else
        return "\<cr>"
    endif
endfunction
imap <expr> <cr> Wrap()

The last line must use imap instead of inoremap.

Answer 1

Simply return "\<plug>empty" This is doing the same basic thing as "\<cr>", returning a string with special characters instead of literal < c r, > etc. Also ensure your <expr> map is not using noremap so vim uses the <Plug> remap. (See the last line in the solution below, using imap instead of inoremap.)

The solution is:

inoremap <Plug>empty "Ends an empty line\<cr>"
function Wrap()
    if getline('.') == ''
        return "\<Plug>empty"
    else
        return "\<cr>"
    endif
endfunction
imap <expr> <cr> Wrap()