Can I do a conditional based on the content of another field in a template

I'm displaying diary items in Perch Runway (as a collection, not using the events app).

Each item has a start date and an end date.

I want to display differently if the start date and the end date are the same, or if they are different. i.e. if it's just one date, then just show the start date, but if they are different, then display both.

So I want something like:

<perch:content id="startdate" type="date" label="Start Date" format="d F Y" suppress="true" />
<perch:content id="enddate" type="date" label="End Date" format="d F Y" suppress="true" />
<perch:if id="startdate" match="eq" value="enddate"><perch:content id="startdate" type="date" label="Start Date" format="d F Y" /></perch:if>

Obviously, the name of the field id in "value" doesn't work. Is there any way to do this?

Alternatively, is there a way to have a date field left blank rather than defaulting to today's date, so I can do an 'if exists' check against the end date

Thanks