Custom validation error messages per rule

[eluser]codex[/eluser]
Second part:

Code:

/**
     * Fetch a single line of text from the language array
     *
     * @access    public
     * @param    string    the language line
     * @return    string
     */
    function line($line = 'default', $rule = 'required')
    {
        return ($line == '' OR ! isset($this->language[$line][$rule])) ? FALSE : $this->language[$line][$rule];
    }