Create a new Mail::Filter
object with the given filter subroutines. Each
filter may be either a code reference or the name of a method to call
on the <Mail::Filter> object.
Add the given @filters to the end of the filter list.
If the first argument is a Mail::Internet object, then this object will be passed through the filter list. If the first argument is a Mail::Folder object, then each message in turn will be passed through the filter list.