my $client = Mail::IMAPClient->new(...);
        # ... search mail box
        my $parsed = Email::MIME->new($client->message_string($msgid));
        my @parts_to_save;
        $parsed->walk_parts(sub { push @parts_to_save, $_[0] });
        # the [0] is the whole message, rest are all parts including nested
        for (@parts_to_save){ print $_->as_string }