You can do $smtp->to(...) multiple times. This is how we have it set up:

@email=qw(address1@host1.com address2@host2.com address3@host3.com);
$smtp->new('my.mailhost');
$smtp->mail('myaddress@myhost.com');
foreach (<@email>) { $smtp->to($_); }
$smtp->datasend("Rule 42 is now in effect.\n");
$smtp->dataend;
$smtp->quit;
[download]

Perhaps not the cleanest, but it works quite nicely.

_{Update: forgot the $smtp->quit;. Also removed commas from @email=qw(...) per comment below.}