getting a form values

Hi all,

I'm new in Drupal :D but learning day to day.

I have the following module (it's an example):

/** 
 * Hook perm
 */
 
function helloworld_perm()
{
	return array('Administer helloworld');
}

/**
 * Hook block
 */
 
function helloworld_block($op = 'list', $delta = 0, $edit = array())
{
	switch($op)
	{
		case 'list':
			$blocks[0] = array(
				'info'       => t('helloworld')
			);			
			return $blocks;
		case 'view':
						
			$block['subject'] = "Hello World";			
			$block['content'] = drupal_get_form('helloworld');
			return $block;
	}
}

function helloworld($params)
{
	
	$form['#method'] = 'post';	
	$form['#action'] = url('helloworld');
	$form['name'] = array(
		'#type' => 'textfield',
		'#size' => '20',
		'#title' => t('Introduce tu nombre'),
		'#default_value' => $params['name'],
	);
	
	$form['submit'] = array('#type' => 'submit', '#value' => t('Greet'));

	//Devolvemos el formulario.
	return $form;
}

Like you can see, it's very simply. I have declared a block with a form content. The action's form goes to "page" node called "holamundo". The code of this node is the following:

if (isset($_POST['name']))
echo "Hello ". $_POST['name']." !!!";

I only want to capture the value of the "nombre" element form. If i use a GET method for the form, it works perfectly, but using POST method $_POST['nombre'] is empty why?, how can I capture the value via POST?

Thanks for all and sorry for my English,

Álvaro