Bug 111265

Until reading section 3.9.1, it looks like section 3.9 advocates setting
all shell variables using setenv / export. Since this is not the case for
at least $SHELL and $TERM (and, I presume, $OSTYPE and $MACHTYPE), new
users might get unexpected results when trying to change variables.

Assuming that the handbook is used as a reference, maybe the information
should be re-organized to avoid misunderstandings.

Fix: 

The explanations of the individual shell variables in section 3.9 could
be moved into the sections discussing their use (such as 3.10, "Editors",
for $EDITOR and 3.9.1, "Changing Your Shell", for $SHELL).

Another option would be to add a warning that some variables should not
be set using setenv / export, or explicitly point out which commands
should be used / link to the relevant documentation.