Manpage of 'regex(7)', from the shell

Today I have read two answers about which regular expressions are supported by less: - Kusalananda mentioned re_format(7) and referenced its manpage as man 7 re_format.

RE_FORMAT(7)           Miscellaneous Information Manual           RE_FORMAT(7)

  NAME
       re_format – POSIX 1003.2 regular expressions

  DESCRIPTION
       Regular expressions (“REs”), as defined in IEEE Std 1003.2 (“POSIX.2”),

- ilkkachu mentioned regex(7) and referenced its manpage by providing a link to a web page instead.

regex(7)            Miscellaneous Information Manual            regex(7)

  NAME
       regex - POSIX.2 regular expressions

  DESCRIPTION
       Regular expressions ("RE"s), as defined in POSIX.2,

I try to figure out how to open the regex(7) manpage from the shell instead of reading it on the web. man regex7, man regex(7), man 7 regex, man7 regex just don't work, and man regex leads to the regex(3) manpage instead.