This is more correct, IMHO.
The old way only sets the default if $FOO is unset; whereas the new way
sets the default if $FOO is unset *or* empty (which is certainly desirable,
if you think of variables like $PAGER).
fi
#v#
-(( ${+PAGER} )) || export PAGER="less"
+export PAGER=${PAGER:-less}
#v#
export MAIL=${MAIL:-/var/mail/$USER}
check_com -c dircolors && eval $(dircolors -b)
# set width of man pages to 80 for more convenient reading
-# (( ${+MANWIDTH} )) || export MANWIDTH=80
+# export MANWIDTH=${MANWIDTH:-80}
# Search path for the cd command
# cdpath=(.. ~)