You can do this in your template using the special ID value
<div id="item<perch:content id="perch_item_index" />"> ... </div>
For each content item output by the template, Perch will increment the number by one. The above would result in:
<div id="item1"> ... </div> <div id="item2"> ... </div> <div id="item3"> ... </div>
One thing that’s important to remember, is that
perch_item_index is a sequential count of the items as they are output. If items are added or removed, or the ordering is changed, then the number output by
perch_item_index will change correspondingly. You can see the docs for more.