CMAKE_MATCH_COUNT
From Get docs
Cmake/docs/3.21/variable/cmake match count
CMAKE_MATCH_COUNT
New in version 3.2.
The number of matches with the last regular expression.
When a regular expression match is used, CMake fills in CMAKE_MATCH_ variables with the match contents. The CMAKE_MATCH_COUNT
variable holds the number of match expressions when these are filled.
© 2000–2021 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.21/variable/CMAKE_MATCH_COUNT.html