Array 1:
$VAR1 = 'CUSTORDS.DAT';
$VAR2 = 'RECEIPTS.DAT';

Array 2:
$VAR1 = 'CUSTORDS.DAT';
$VAR2 = 'ONHAND.DAT';
$VAR3 = 'RECEIPTS.DAT';

Count:
$VAR1 = 'ONHAND.DAT';
$VAR2 = '1';
$VAR3 = 'RECEIPTS.DAT';
$VAR4 = '2';
$VAR5 = 'CUSTORDS.DAT';
$VAR6 = '2';

Union:
$VAR1 = 'ONHAND.DAT';
$VAR2 = 'RECEIPTS.DAT';
$VAR3 = 'CUSTORDS.DAT';

Intersection:
$VAR1 = 'RECEIPTS.DAT';
$VAR2 = 'CUSTORDS.DAT';
 
Difference:
$VAR1 = 'ONHAND.DAT';