How do I make regex work properly?

[superusercode]

i.e. https://rvgl.org/
I have checkver set to

"regex": "<p class=\"vernum\">Current version: \\d{2}\\.\\d{4}[a-z]-?\\d*"

fails Calinou/scoop-games#936
verified that it is actually there using page source.

I still had failures even when I only did the regex for the version numbers. I added the html in an attempt to see if I needed to include more to match to. I also used \s for whitespace

[superusercode]

These do not work in the manifests, but they work outside of them