Man pages matching name curlopt_fnmatch_function in section 3:

CURLOPT_FNMATCH_FUNCTION.3.en	debian 10 / libcurl4-doc
CURLOPT_FNMATCH_FUNCTION.3.en	debian 11 / libcurl4-doc
CURLOPT_FNMATCH_FUNCTION.3.en	debian 12 / libcurl4-doc