Man pages matching name libmawk_register_function in section 3libmawk:

libmawk_register_function.3libmawk.en	debian 10 / libmawk1
libmawk_register_function.3libmawk.en	debian 11 / libmawk1
libmawk_register_function.3libmawk.en	debian 12 / libmawk1
libmawk_register_function.3libmawk.en	debian 13 / libmawk1t64