Craft 1.4 - Import Matrix block to entry.

gistfile1.php

<?php
/**
 * Matrix Block
 */
if( isset($importEntry->post) )
{
    $matrixData = array(
        'pageContent' => array(
            'type'    => 'text',
            'enabled' => true,
            'fields'  => array(
                'text' => $post,
            ),
        ),
    );

    // Save the new Matrix data
    $entry->setContentFromPost( $matrixData );
}
?>