use Mail::Sender;

my $text_msg = "foo";
my $html_msg = "<p>foo</p>";

my $sender = new Mail::Sender
{  smtp => '127.0.0.1',
   from => "Teacher <me\@mydomain.com>",
}
 
$sender->OpenMultipart(
  { to        => "$rcpt",
    subject   => "$subject",
    multipart => "mixed",
  })
  or die "Can't Open message: $sender->{'error_msg'}\n";

$sender->Part( { ctype => 'multipart/alternative' });
$sender->Part(
  { ctype       => 'text/plain',
    disposition => 'NONE',
    msg         => "$text_msg\n"
  });
$sender->Part(
  { ctype       => 'text/html',
    disposition => 'NONE',
    msg         => "$html_msg\n"
  });

$sender->Close()
  or die "Failed to send message: $sender->{'error_msg'}\n";