Programmatically getting a list of variables

Is it possible to get a list of declared variables with a VimL (aka VimScript) expression? I'd like to get the same set of values that will be presented for a command using -complete=expre开发者_StackOverflow中文版ssion. The goal is to augment that list for use in a user-defined command completion function.

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You can use g: as a dictionary that holds all global variables, so:

let globals = keys(g:)

will give you all the names. The same applies to the other scopes: b:, s:, w:, etc. See :help internal-variables for the complete list.

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You can get something similar using keys of g:, b:, t:, w: and v: dictionaries, but beware of the following facts:

1. There is no equivalent to this dictionaries if you want to complete options.
2. Some variables like count (but not g:count or l:count), b:changedtick and, maybe, others are not present in this dictionaries.
3. Some vim hacker may add key @@@ to dictionary g:, but it won't make expression g:@@@ valid variable name (but adding 000 there will). Though g:["@@@"] will be a valid expression.