my $clause1 = '';
if ($some_condition) {
    $clause1 = <<'END_SQL';
    AND a.somedata5 <= ?
    AND [...]
END_SQL

my $clause2 = '';
if ($some_condition) {
    $clause2 = <<'END_SQL';
    AND b.somedata6 >= ?
    [...] 
END_SQL

my $order_by = '';
if ($some_condition) {
    $order_by = <<'END_SQL';
    ORDER BY somedata7
END_SQL

my $sql = <<END_SQL;
    SELECT a.somedata1,
           a.somedata2,
           a.somedata3,
           [...]
    FROM table1 a,
         table2 b,
         table3 c
    WHERE a.somedata4 > ?
$clause1
$clause2
$order_by
END_SQL