[CMake] STRING REGEX MATCH

[Brandon J. Van Every]

How can I extract only a number [0-9]+ in 1 regex step?  Seems like I 
should be able to do it with parentheses, but it's not working.  The 
following is clear, and works, but what's the short way?

    STRING(REGEX MATCH "Version [0-9]+" VERSION_STRING ${CHICKEN_BANNER})
    STRING(REGEX MATCH "Build [0-9]+" BUILD_STRING ${CHICKEN_BANNER})
    # Haven't figured out how to do this in one regex.
    STRING(REGEX MATCH "[0-9]+" VERSION_NUMBER ${VERSION_STRING})
    STRING(REGEX MATCH "[0-9]+" BUILD_NUMBER ${BUILD_STRING})

${CHICKEN_BANNER} is

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