Google seems to be testing the ability to filter by perspectives. Google is testing a button to filter your query by the perspectives results.

This was spotted by Saad AK, he posted a video on Twitter, here is a GIF of that video in action:

Here is a still screenshot:

About a year ago, Google started to show perspectives and it officially went live a couple of months ago.

I find it interesting that this is being tested as a search filter…

Forum discussion at Twitter.