unexported $vars seen thru () docs

[Dan Jacobson]

man page:
       (list) list  is  executed  in  a  subshell.
ok, don't we have to export things to have them heard in a subshell?
$ m=p;(echo $m)
p
       $      Expands to the process ID of the shell.  In a  ()  subshell,  it
              expands  to  the  process  ID of the current shell, not the sub-
              shell.
OK, then also mention that other unexported $vars can be seen thru () unless
overwritten in the subshell

$ m=p;bash -c set|grep =p
$ m=p;(set)|grep =p
m=p
so it is a special subshell