Pir's Whim

The designation of friend or foe is only relevant to the spell that asks you to choose. A player you call your friend doesn’t become your teammate, and the next “friend or foe” spell you cast could name that player your foe.

Friends perform their specified actions before foes. This means that a friend’s action may cause a triggered ability of a foe’s permanent to trigger before that foe’s action causes that permanent to leave the battlefield.

When Pir’s Whim resolves and your friends perform their actions, first the next friend in turn order (or, if it’s a friend’s turn, that friend) searches their library for a land without revealing the card they choose, then each other friend in turn order does the same. Then all the lands are put onto the battlefield at the same time.