Annex E (informative) Conformance with UAX #31 [uaxid]

E.4 R3 Pattern_White_Space and Pattern_Syntax characters [uaxid.pattern]

UAX #31 describes how languages that use or interpret patterns of characters, such as regular expressions or number formats, may describe that syntax with Unicode properties.
C++ does not do this as part of the language, deferring to library components for such usage of patterns.
This requirement does not apply to C++.