Here's a basic sample that sends a message, without a file attachment. Net::SMTP is the key.

#!/usr/local/bin/perl -w

use strict;
use Net::SMTP;

{
  my $sender = 0;

  $sender = Net::SMTP->new ('smtp.mailserver.pm');
  $sender->mail ('perlmonk@themonastery.org');
  $sender->to ('goddesses@themonastery.org');
  $sender->data ();
  $sender->datasend ("From: perlmonk\@themonastery.org\n");
  $sender->datasend ("To:   goddesses\@themonastery.org\n");
  $sender->datasend ("Subject: Promotions\n");
  $sender->datasend ("\n");
  $sender->datasend ("Please vote my articles up, I need the XP"\n\n")
+;
  $sender->dataend;
  $sender->quit;
}
[download]

I'll have to let other people tell/show you how to send a file attachment, although I would take a look at Mail::Sender. It looks pretty easy to use. I've never had to mess with that.

--Chris

Originally posted as a Categorized Answer.