set_value method with edit form

[eluser]iConTM[/eluser]
For a backend I'm using CIs formvalidation methods:

Code:

<input type="text" name="email" value="<?php echo set_value('email'); ?>" />

When a user wants to edit a record, the value of the inputfield above must be filled in with data from the database.

How can I determine which data the set_value method returns?

Any ideas?