<select name="<!-- TMPL_VAR NAME=SELECT -->">
<!-- TMPL_LOOP NAME=VALUES -->
  <option value="<!-- TMPL_VAR NAME=VALUE -->" <!-- TMPL_IF NAME=SELECTED -->selected<!-- /TMPL_IF -->><!-- TMPL_VAR NAME=VALUE --></option>
<!-- /TMPL_LOOP -->
</select>

my $selectname = "xy";
my $xy = 'selectedValue';
my @array;

[... Datenbankverbindung und Abfrage ...]

while(my ($value) = $sth->fetchrow_array()){
   my $selected = $value eq $xy ? 1 : 0;
   push(@array,{VALUE => $value, SELECTED => $selected});
}

$template->param({
        SELECT => $selectname,
        VALUES => \@array,
                      });