From http://www.w3schools.com (Copyright Refsnes Data)

WML Variables

Variables

When a user switches from card to card in a deck, we need to store data in variables. WML variables are case sensitive.

When someone executes a task (like go, prev, and refresh), the setvar element can be used to set a variable with a specified value.

The following example will create a variable named i with a value of 500:

<setvar name="i" value="500"/>

The name and value attributes are required.

Variables can also be set through an input element (like input, select, option, etc.).

The following example will create a variable named schoolname:

<card id="card1">
<select name="schoolname">
<option value="HTML">HTML Tutorial</option>
<option value="XML">XML Tutorial</option>
</select>
</card>

To use the variable we created in the example above:

<card id="card2">
<p>You selected: $(schoolname)</p>
</card>