+
+Note: Even when FINISH-FUNC is present, a future is still returned except that
+it yields no value (since the value is passed to FINISH-FUNC). Call
+`async-get' on such a future always returns nil. It can still be useful,
+however, as an argument to `async-ready' or `async-wait'.
+
+## async-start-process
+
+ async-start-process NAME PROGRAM FINISH-FUNC &rest PROGRAM-ARGS
+
+Start the executable PROGRAM asynchronously. See `async-start'. PROGRAM is
+passed PROGRAM-ARGS, calling FINISH-FUNC with the process object when done.
+If FINISH-FUNC is nil, the future object will return the process object when
+the program is finished.
+
+## async-get
+
+ async-get FUTURE
+
+Get the value from an asynchronously function when it is ready. FUTURE is
+returned by `async-start' or `async-start-process' when its FINISH-FUNC is
+nil.
+
+## async-ready
+
+ async-ready FUTURE
+
+Query a FUTURE to see if the ready is ready -- i.e., if no blocking
+would result from a call to `async-get' on that FUTURE.
+
+## async-wait
+
+ async-wait FUTURE
+
+Wait for FUTURE to become ready.
+
+## async-inject-variables
+
+ async-inject-variables INCLUDE-REGEXP &optional PREDICATE EXCLUDE-REGEXP
+
+Return a `setq' form that replicates part of the calling environment. It sets
+the value for every variable matching INCLUDE-REGEXP and also PREDICATE. It
+will not perform injection for any variable matching EXCLUDE-REGEXP (if
+present). It is intended to be used as follows:
+
+ (async-start
+ `(lambda ()
+ (require 'smtpmail)
+ (with-temp-buffer
+ (insert ,(buffer-substring-no-properties (point-min) (point-max)))
+ ;; Pass in the variable environment for smtpmail
+ ,(async-inject-variables "\\`\\(smtpmail\\|\\(user-\\)?mail\\)-")
+ (smtpmail-send-it)))
+ 'ignore)