docs(styleguide): update examples of quoting

Author: akinomyoga

doc/styleguide.md

@@ -141,23 +141,24 @@ shell expansions.
 In the following contexts, the quoting to suppress word splitting and pathname
 expansions are not needed.
 
-- The right-hand sides of variable assignments ... `v=$var`
-- The arguments of conditional commands ... `[[ $var ]]`
-- The argument specified to `case` statement ... `case $var in foo) ;; esac`
+- The right-hand sides of variable assignments ... `v=WORD` (e.g. `v=$var`)
+- The arguments of conditional commands ... `[[ WORD ]]` (e.g. `[[ $var ]]`)
+- The argument specified to `case` statement ... `case WORD in foo) ;; esac`
+  (e.g. `case $var in foo) ;; esac`)
 
 In bash-completion, we do not quote them by default.  However, there are
 exceptions where the quoting is still needed for other reasons.
 
 - When the word *directly* contains shell special characters (space, tab,
   newline, or a character from ``;|&()<>\\$`'"#!~{``), these characters need to
-  be quoted.  The "*directly*" means that the characters produced by the shell
-  expansions, such as `$var`, are excluded.  For example, when one wants to
-  include a whitespace as a part of the value of the word, the right-hand side
-  can be quoted as `v="a b"`.
+  be quoted.  The "*directly*" means that the special characters produced by
+  shell expansions are excluded here.  For example, when one wants to include a
+  whitespace as a part of the value of the word, the right-hand side can be
+  quoted as `v="a b"`.
 - An empty word (i.e., the word whose value is an empty string) is specified by
-  `""`.  The right-hand sides of assignments technically can be an empty string
-  as `var=`, but we still use `var=""` there because `shellcheck` suggests that
-  e.g. `var= cmd` is confusing with `var=cmd`.
+  `""`.  The right-hand side of an assignment technically can be an empty
+  string as `var=`, but we still use `var=""` there because `shellcheck`
+  suggests that e.g. `var= cmd` is confusing with `var=cmd`.
 - `$*` and `${array[*]}` need to be always quoted because they can be affected
   by the word splitting in bash <= 4.2 even in the above contexts.
 - In the following contexts, double-quoting of shell expansions is needed