“Buy 10, Get 1” loyalty programs are directly descended from paper punchcard programs and serve a general purpose. They are especially effective for transactions that are always about the same (i.e. coffee, pizza and the movies).

But how do you spur more buying and more frequent buying when transactions are highly variable? This was a question posed last year by Southwest Airlines when it shifted its loyalty program from trips to dollars spent.

Now Perka, a 28 person, national loyalty provider based in Portland, OR and New York, is adding a “Flex Card” option for its loyalty efforts as well. Perka’s Flex Card program enables local merchants to not only tally different kinds of spending, but it also enables them to set a variety of thresholds for rewards (i.e., 50 points to a shirt, 500 points to a birthday party, etc.)

Co-Founder Robert Bethge tells us the Flex card program was soft launched in October, and costs merchants $50 per month, as opposed to $35 for the standard electronic punchcard. Currently, 50 merchants are on the flex card option, while 450 take the punchcard.

Bethge adds that a key advantage of the Flex card program, he notes, is that it leverages the company’s ability to read directly off Point of Sales systems, adding many additional “closed loop” verification capabilities.