Sorry for not coming back here earlier, I was kind of busy with other devotions.

Anyway, this solved my problem :

use Authen::SASL qw(Perl);
use MIME::Lite;
[download]

For me it works, without appearing to have any deleterious side-effects in how the program runs or how much time it takes.

It would appear that something is amiss in at least the Debian Lenny packages for Authen::SASL::XS*. But my knowledge of such arcane things being what it is, I could not tell what, nor do I know exactly what to do about it for the benefit of the gentile multitude.

P.S. I also tried to re-install the Authen::SASL::XS* packages using "perl -MCPAN" directly, but that did not solve the problem either. Which means I remain just as clueless.