Miscellaneous improvements

manuscript/chapter6.txt

@@ -3,14 +3,28 @@
 ## Assign and access a variable using a variable
 
 ```shell
-hello_world="test"
+$ hello_world="value"
 
 # Create the variable name.
-var1="world"
-var2="hello_${var1}"
+$ var="world"
+$ ref="hello_$var"
 
-# Print the value of the variable name stored in 'hello_$var1'.
-printf '%s\n' "${!var2}"
+# Print the value of the variable name stored in 'hello_$var'.
+$ printf '%s\n' "${!ref}"
+value
+```
+
+Alternatively, on `bash` 4.3+:
+
+```shell
+$ hello_world="value"
+$ var="world"
+
+# Declare a nameref.
+$ declare -n ref=hello_$var
+
+$ printf '%s\n' "$ref"
+value
 ```
 
 <!-- CHAPTER END -->