perch:email field for autoresponder message?

I'm setting up an autoresponder in the Forms App using an HTML template. I am aware of two special values for HTML email templates:

• <perch:email id="email_subject" />
• <perch:email id="email_message" />

Might there be another to populate the "Response introduction text" in the Autoresponse section of the form settings?

Cheers