Very rarely, you may get a .wps (WordPerfect) file as an attachment instead of a .pdf, .docx, or .pages file. You can ask the sender to re-send it in another format, or you can pay WordPerfect US$220 to install WordPerfect to open one attachment... or you can try to open the .wps file.
Won't work in Google Drive
Won't work in Microsoft Word
Won't work in Page
It does work in LibreOffice!!!
Here's the solution: if you don't want to discard the attachment or have the sender re-send in another format, open the .wps file in LibreOffice. The formatting may not be exactly the same as in WordPerfect, but it will be pretty close.
And the best part is that LibreOffice is cross-platform (it works on Mac, Windows, and Linux).