Here is an answer who use the textarea as asked.
JSFiddle http://jsfiddle.net/7ZHcL/
HTML
<form action="demo.html" id="myForm">
<p>
<label>Variable name:</label>
<textarea id="varWanted" name="varWanted" cols="30" rows="1"></textarea>
</p>
<input type="submit" value="Submit" />
</form>
<div id="result"></div>
JQuery
$(function () {
// Handler for .ready() called.
var variables = {
'money': '300$',
'date_now': new Date()
}
//Detect all textarea's text variation
$("#varWanted").on("propertychange keyup input paste", function () {
//If the text is also a key in 'variables', then it display the value
if ($(this).val() in variables) {
$("#result").html('"' + $(this).val() + '" = ' + variables[$(this).val()]);
} else {
//Otherwise, display a message to inform that the input is not a key
$("#result").html('"' + $(this).val() + '" is not in the "variables" object');
}
})
});