Jenkins declarative pipeline env var definition

gistfile1.txt

environment {
    DEVELOP_TAG = "Build${BUILD_NUMBER}"
    RELEASE_TAG = sh(
            script: "printf \$(grep CLIENT_VERSION_MAJOR CMakeLists.txt | head -n1 | cut -d ' ' -f2 | sed 's/)//g' | tr -d '\\n' | tr -d '\\r').\$(grep CLIENT_VERSION_MINOR CMakeLists.txt | head -n1 | cut -d ' ' -f2 | sed 's/)//g' | tr -d '\\n' | tr -d '\\r').\$(grep CLIENT_VERSION_REVISION CMakeLists.txt | head -n1 | cut -d ' ' -f2 | sed 's/)//g' | tr -d '\\n' | tr -d '\\r') | sed 's/ //g'",
            returnStdout: true
    )
    GIT_TAG_TO_USE = "${DEVELOP_TAG}"
    GIT_COMMIT_SHORT = sh(
            script: "printf \$(git rev-parse --short ${GIT_COMMIT})",
            returnStdout: true
    )
    CURRENT_DATE = sh(
            script: "printf \"\$(date '+%F %T')\"",
            returnStdout: true
    )
}