A variable variable looks like this: $$var So, if $var = 'foo' and $foo = 'bar' then $$var would contain the value 'bar' because $$var can be thought of as $'foo' which is simply $foo which has the value 'bar'. Variable variables sound like a cryptic a useless concept, but they can be useful sometimes. For example, if we have a configuration file consisting of configuration directives and values in this format: Then it is very easy to read this file and create corresponding variables: ]]> Along the same lines as variable variables, you can create compound variables and variable functions. ]]>