The SET command sets the value of a variable.
SET variable TO expression
The expression is evaluated in the context of each product in the Working Set and each product stores its own value for the variable. If, however, the variable is a global variable, the same value is stored in the variable for each product.
Examples:
WHERE ebay.active
SET $title TO ebay.title
eval $title
The above commands select all products which have active listings on eBay then set the $title variable for each of the product's to the product's title. It then lists all of the selected products and displays the value of $title for each product.