• document the pipeline thing better

• set -o {posix,sh} also turns off the other, like {emacs,gmacs,vi}

mksh.1

@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.213 2010/01/28 15:23:03 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.214 2010/01/28 15:33:11 tg Exp $
 .\" $OpenBSD: ksh.1,v 1.129 2009/05/28 06:09:06 jmc Exp $
 .\"-
 .\" Copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
@@ -3591,12 +3591,12 @@ for pristine I/O.
 The inner loop will be executed in a subshell and variable changes
 cannot be propagated if executed in a pipeline:
 .Bd -literal -offset indent
-foo \*(Ba bar \*(Ba while read foo; do ...; done
+bar \*(Ba baz \*(Ba while read foo; do ...; done
 .Ed
 .Pp
 Use co-processes instead:
 .Bd -literal -offset indent
-foo \*(Ba bar \*(Ba&
+bar \*(Ba baz \*(Ba&
 while read \-p foo; do ...; done
 exec 3\*(Gt&p; exec 3\*(Gt&\-
 .Ed
@@ -3913,7 +3913,9 @@ Enable a somewhat more
 ish mode.
 As a side effect, setting this flag turns off
 .Ic braceexpand
-mode, which can be turned back on manually.
+mode, which can be turned back on manually, and
+.Ic sh
+mode.
 .It Ic sh
 Enable
 .Pa /bin/sh
@@ -3921,11 +3923,13 @@ Enable
 mode.
 Automatically enabled if the basename of the shell invocation begins with
 .Dq sh
-and this autodetection feature was requested at compilation time
+and this autodetection feature is compiled in
 .Pq not in MirBSD .
 As a side effect, setting this flag turns off
 .Ic braceexpand
-mode, which can be turned back on manually.
+mode, which can be turned back on manually, and
+.Ic posix
+mode.
 .It Ic vi
 Enable
 .Xr vi 1 Ns -like
@@ -5980,6 +5984,13 @@ x=$(case $foo in bar) echo $bar ;; *) echo $baz ;; esac)
 .Pp
 Patches welcome.
 .Pp
+The parts of a pipeline, like below, are executed in subshells.
+Thus, variable assignments inside them fail.
+This is actually a feature; use co-processes instead.
+.Bd -literal -offset indent
+foo \*(Ba bar \*(Ba read baz    # will not change $baz
+.Ed
+.Pp
 This document attempts to describe
 .Nm mksh\ R39+devel
 and up,