Gem::BundlerVersionFinder.bundle_config_version

# File tmp/rubies/ruby-4.0.0/lib/rubygems/bundler_version_finder.rb, line 84
def self.bundle_config_version
  config_file = bundler_config_file
  return unless config_file && File.file?(config_file)

  contents = File.read(config_file)
  contents =~ /^BUNDLE_VERSION:\s*["']?([^"'\s]+)["']?\s*$/

  $1
end