my $SELECT = "SELECT * FROM mytable WHERE usercode=? AND unsubscribedby = ''";
  my $UPDATE = "UPDATE mytable SET subscribed = '0', unsubscribedby = 'SYSTEM' WHERE usercode=? AND unsubscribedby = ''";
for (@usercodelist) {
  my $sth = $DBH->prepare($SELECT);
  my $q = $sth->execute($_);
  while (my $r = $q->fetchrow_hashref()) {
    print "Matched $$_{usercode}\n";
  }
  $sth = $DBH->prepare($UPDATE);
  $sth->execute($_) 
    or die "<div>Could not execute SQL statement ... maybe invalid?</div><div>$!</div>";
  $sth->finish();
}