Is the perl sending the email?? Or are you using the POST enctype mailto method from an html document? Big difference on options here.
If it's a perl script which answers the form submit button and sends an email; just edit your mail message to include a from line from:noreply@mail.com in the message head.
If you want to remove the server name in the message head itself (Viewable in a mail client by clicking view source you'll have to change that in your server dns settings).