"It is a Ponzi scheme for these young people. The idea that they're working and paying into Social Security today, that the current program is going to be there for them, is a lie," Perry said. "It is a monstrous lie on this generation, and we can't do that to them."
Nick Baumann at Mother Jones has a nice round-up of why Social Security is actually not a Ponzi scheme, culminating in the Venn diagram above.
But more to Melissa's point and the trope that Perry is speaking in code is this point from Jonathan Bernstein on the Plum Line blog:
Of course, this has nothing whatsoever to do with a Ponzi scheme, which involves deliberate and outright fraud. It's irresponsible to say that Social Security won't be "there for them" when, in fact, the only way that will happen is if politicians choose to eliminate it.
Social Security is only a Ponzi scheme if you make it one by destroying it. If this is your intention as a candidate, and as a candidate it is also your intention, your expectation even, to win the office of the presidency, then it makes sense that your present view of Social Security is distorted by the damage you intend to inflict on it.