CMAKE_MATCH_COUNT
The number of matches with the last regular expression.
When a regular expression match is used, CMake fills in CMAKE_MATCH_<n> variables with the match contents. The CMAKE_MATCH_COUNT variable holds the number of match expressions when these are filled.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.5/variable/CMAKE_MATCH_COUNT.html