To concatenate string with something else, use the period (.) symbol. Example:
" string with stringecho "Hello" . " " . "World" " => "Hello World"" string with variablesecho "Hello" . name => "Hello Smith"" string with argument variablesecho "Hello" . a:name => "Hello Sarah"Any types will of variables will be automatically converted back to string.
That's all about string concatenation in vimrc.