[jwilk]

There are many awk implementations, so whether that reference is decent or not may vary. It looks like on BSDs, there's so such section at all.

[georgia_peach]

Tested on Linux, OpenBSD, & Mac:

POSIX: man 7 re_format

PCRE: man pcrepattern

PCRE2: man pcre2pattern

PCRE may be a "works on my machine" thing, but POSIX should be there.