[monolithed]

<script type="text/javascript">
window.onload = function() {
    var forma = document.forma,
        input = forma.input, i = input.length, 
        array = ['query1', 'query2', 'query3'];
    
    while(i--) {
        input[i].onchange = function(i) {
            return function() {
                forma.text.value = array[i];
            };
        }(i);
    }     
};
</script>

<form name="forma" action="" method="post">
    <input type="radio" name="input" />Запрос 1
    <input type="radio" name="input" />Запрос 2
    <input type="radio" name="input" />Запрос 3<br />
    <textarea rows="6" cols="26" name="text" /></textarea>
</form>

или в такой нотации:

<script type="text/javascript">
window.onload = function() {
    var forma = document.forma,
        input = forma.input,i = input.length, 
        array = {
            value1 : 'query1',
            value2 : 'query2',
            value3 : 'query3'
        };
    
    while(i--) {
        input[i].onchange = function(i) {
            return function() {
                forma.text.value = array[this.value];
            };
        }(i);
    }
};
</script>

<form name="forma" action="" method="post">
    <input type="radio" name="input" value="value1" />Запрос 1
    <input type="radio" name="input" value="value2" />Запрос 2
    <input type="radio" name="input" value="value3" />Запрос 3<br />
    <textarea rows="6" cols="26" name="text"></textarea>
</form>