[io grant] Point out my $*CWD = chdir … is an error

Will eventually write a separate paragraph on all the evils of $*CWD
and link to it from all the problematic areas.

Author: zoffixznet

doc/Type/IO.pod6

@@ -40,6 +40,12 @@ By default, only C<:d> test is performed.
     chdir :r, :w '/tmp'; # … check its .r and .w are True
     chdir '/not-there';  # returns Failure
 
+Note that the following construct is a mistake:
+
+    my $*CWD = chdir '/tmp/';
+
+Use L«C<indir>|/routine/indir» instead.
+
 =head2 sub &*chdir
 
 Defined as:
@@ -63,6 +69,16 @@ to specify which file tests to perform.
     &*chdir('/tmp');  # change $*CWD and process's current directory to '/tmp'
     &*chdir('/not-there'); # returns Failure
 
+Note that the following construct is a mistake:
+
+    my $*CWD = &*chdir('/tmp');
+
+Use the following, instead; or see L«C<indir>|/routine/indir» if
+you do not need to change process's current directory:
+
+    temp $*CWD;
+    &*chdir('/tmp');
+
 =head2 sub indir
 
 Defined as: