The similarity is this. They both emphasize a relationship between two events.
With conditionals, the occurrence of one event, for example, depends on the other event happening.
Conditional: We'll go to the park if it doesn't rain.
Event#1: It doesn't rain
Event#2: We'll go to the park
With the perfect aspect, one event occurs before another in time.
Perfect: We had eaten before you arrived.
Event#1: We had eaten
Event#2: you arrived
Hope that helps.
All the best.