+-------------+ +------------------+ 
| Products    | | Supplier_Product | 
+-------------+ +------------------+
| PNO | PNAME | | SNO     | PNO    |
+-----+-------+ +---------+--------+
| P1  | Screw | | S1      | P1     | 
| P1  | Screw | | S1      | P1     | 
| P1  | Screw | | S1      | P2     | 
| P2  | Screw | +------------------+ 
+-------------+

##</code><code>##

SELECT parts.pno 
FROM   parts
WHERE  parts.pname = 'Screw'
   OR  parts.pno IN
      (SELECT supplier_parts.pno
       FROM   supplier_parts
       WHERE  supplier_parts.sno = 'S1')

##</code><code>##

SELECT DISTINCT parts.pno 
FROM   parts
WHERE  parts.pname = 'Screw'
   OR  parts.pno IN
      (SELECT supplier_parts.pno
       FROM   supplier_parts
       WHERE  supplier_parts.sno = 'S1')

##</code><code>##

use warnings;

my $foo = undef;
print "This is some ", $foo, "\n";

##</code><code>##

perl somescript.pl 1 2 three four

##</code><code>##


my $sum;
$sum += $_ foreach @ARGV;
print $sum, "\n";