With an OR 2-scan, you can avoid the negation. Here's how I'd do it in APL: {⍵⌿⍨2∨⌿0⍪' '≠⍵}. In general, I find that boolean 2-scans pop up quite a bit in real-world APL usage. It's worth working through them. I have a short article [0] on the subject, if you're interested.

It's also worth thinking through how all 16 boolean operators work on boolean masks. E.g. what do msk≠msk2, msk<msk2, msk≤msk2 etc. mean? In my experience, the important part is to find crisp domain-specific meanings for these patterns. In general, really, that's how you gain APL fluency. In the same way that reading fluency requires chunking so that letters "disappear", APL fluency requires familiarity with semantic phrases, so you stop thinking in the individual symbols.

[0]:https://blog.wilsonb.com/posts/2023-07-24-suggestivity-and-i...