Livecheck regex with version in url path

[Steven Smith]

> you need to find a URL that doesn't contain the version number for MacPorts to download. For ghc, https://downloads.haskell.org/~ghc/ looks like a reasonable URL to use. Of course you'll have to change the regex to match directories rather than files.

Would you or someone please provide a one-liner on how to do that? The stuff I’ve tried hasn’t worked.
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