Its only relevant which is the name of the variable you use inside <variable> so you can use it later as $_GET[‘variable’]
to do what you said use something like
'rules'=>array(
'module/<module:\w+>/<controller:\w+>/<action:\w+>'=>'<module>/<controller>/<action>',
//now do the following just so you see what I meant
'module/<m:\w+>/<c:\w+>/<a:\w+>'=>'<m>/<c>/<a>',
)
By the way, you can use these variable you set inside <var> by doing later $_GET[‘var’], its useful many times, to for example, get an id setting rules like
'<c:\w+>/<a:\w+>/<id:\d+>'=>'<c>/<a>',
'<c:\w+>/<a:\w+>/<id:\d+>-<title:\w+>'=>'<c>/<a>',
'<c:\w+>/<id:\d+>-<title:\w+>'=>'<c>',
//and in your app
//url will be myController/myAction/12-myTitle
echo $_GET['id'];
echo $_GET['title'];