Instead of re-reading your template file each time (remember - disk I/O is expensive), read the template once and then manipulate a copy for each email you send. Take a look at the following (very rough code)...

$sendthis = <FILE>;
foreach my $mailrecord (@list_of_addresses_and_names_etc) {
  my $msg = $sendthis;
# manipulate the $msg and send
}
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