[racket] thread-through ?

I looked in racket documentation and discussion archives for a
thread-through function as illustrated below but without success.
Any suggestions where I should look? OR please explain that line below only.
Looks like it is declaring thread-safe variables x e and any others I care
to list.  Is that correct?

;Use a macro:
(thread-through x e …)
==
(let* ([x e] …) x)
;--------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20150220/774647f5/attachment.html>