This is a kind of bug report for pandoc==2.15 specific.

I have faced strange behavior of lua filter, which processes Link, with pandoc==2.15. After some research, I found this is kinda related to issue #7639 (https://github.com/jgm/pandoc/issues/7639).

So now I am trying to put a message that filter won't work with pandoc==2.15 when it is so, like following code snippet, but Lua filter (or Lua subsystem) doesn't detect pandoc's version either.

```lua

if PANDOC_VERSION=={2,15} then
print("this filter wont work with pandoc==2.15")
end

```

The message won't appear with pandoc==2.15. On the other hand, `tostring(PANDOC_VERSION)` returns "2.15". So if anyone trying to handle Link with pandoc==2.15, use tostring(PANDOC_VERSION) to filter out pandoc version.