{action primes, reverse} ... {/action} applies one of the sequence actions to a list and iterates what comes out, the current value in {$sequence}. The list is usually a store pushed earlier, but a range ({action sum, '31..40'}, 355) or a type with its options ({action:reverse prime, rows=5}, 11 7 5 3 2) works too. Store and action may be written in either order, and the prefix form names the action in the tag: {action:reverse primes}, {action:shift primes, 2}.

The actions are those of {sequence}: orderings (reverse, sort, shuffle), selections (first=n, last=n, element, slice), aggregates that leave a single value (sum, average, median, count, minimum, maximum) and dedup. An aggregate's value is also there under the action's name - {$sum}.

The store is read, not rewritten: after {action primes, reverse} the store still holds its original order - except for shift and pop, which take values out of it. To transform a store in place, use {resume}; to apply several actions and plays to a store at once, {pull}.