How to read the value of Maplocalleader?

Question

The command map localleader are explained very nicely here. How do I read the current value of the <localleader> thingy? Is this a variable or what?

Answer 1

From :h maplocalleader:

                                        <LocalLeader> maplocalleader
<LocalLeader> is just like <Leader>, except that it uses "maplocalleader"
instead of "mapleader".  <LocalLeader> is to be used for mappings which are
local to a buffer.

Recursing on to :h <Leader> (which is just above this paragraph):

                                        <Leader> mapleader
To define a mapping which uses the "mapleader" variable, the special string
"<Leader>" can be used.  It is replaced with the string value of "mapleader".
If "mapleader" is not set or empty, a backslash is used instead.  Example: 
        :map <Leader>A  oanother line<Esc>
Works like: 
        :map \A  oanother line<Esc>
But after: 
        :let mapleader = ","
It works like: 
        :map ,A  oanother line<Esc>

So, mapleader is a variable, and therefore maplocalleader is too.

The tricky part, of course, is that neither is set by default - and so Vim uses \ as the leader. If you try to examine the value of these two variables, by e.g., let maplocalleader or echo mapleader, Vim will just throw an error:

E121: Undefined variable: mapleader

How do you set it? The <Leader> help quoted above has an example:

let mapleader = ","

Similarly, for example:

let maplocalleader = "_"