use Mail::Box::Manager;
use MIME::Base64::Perl;

[...]
my $msg = $folder->message(0);
if ($msg->isMultipart) {
	my @parts = $msg->parts;
	foreach (@parts) {
		if ($_->contentType eq "image/jpeg") {
                    (my $body = $_->body) =~ s/\n//g;
                    my $jpg = decode_base64($body);
                }
        }
}