use DBI;
my $dbi = DBI->connect(...);

sub select_scalar {
  my ($dbi, $sql) = @_;
  my $sth = $dbi->prepare($sql);
  $sth->execute();
  my $r = $sth->fetch_row_array();
  return $r->[0];
}

my $q1 = "select 1 from dual where 'ä' = chr(228)";
my $q2 = $q1.chr(1024);
chop($q2);

print "q1 eq q2? ", ($q1 eq $q2 ? "yes" : "no"), "\n";

my $r1 = select_scalar($dbi, $q1);
print "r1 = $r1\n";
my $r2 = select_scalar($dbi, $q2);
print "r2 = $r2\n";