It seems you have found something like Using MIME::Lite with TLS or the gmail.pm that is linked to in that thread.

Without looking at it in detail I would guess that you might copy the method referenced there and the following two lines into your own code. This would overload/overwrite/substitute the corresponding method in Mime::Lite similar to what you would do if you subclassed Mime::Lite and defined the method in that subclass

You also need to install any modules needed by that method and it might work.