my $sql = "select type from bilder where id =?";
    my $sth = $dbh->prepare($sql);
    $sth->execute( $q->param('id') );
    my $error = 0;
    my $type = $sth->fetchrow || ( $error = 1 );
    $sql = "select data from bilder where id =?";
    $sth = $dbh->prepare($sql);
    $sth->execute( $q->param('id') );
    my $data = $sth->fetchrow();
    binmode(STDOUT);
    ...