Experts and BHG readers answer.
It has indeed been a baffling winter. The perennials will recover for the most part and get into their stride with new growth once the weather settles. Some plants that were set out late in the fall may not make it, as they don't have an established root syetem, but for the most part there is no reason to worry. Next winter apply a winter mulch of evergreen boughs as soon as the ground freezes to mitigate the effects of thawing and refreezing.