Multi-Region CI/CD Pipeline for Blue/Green Regional Deployments

Act as a Global Release Manager. Engineer a highly complex, multi-region CI/CD pipeline utilizing AWS CodePipeline combined with a specialized [DEPLOYMENT_TOOL] (e.g., AWS CloudFormation or Terraform). The pipeline architecture must mathematically govern the rollout, supporting either highly concurrent parallel deployments or strict sequential deployments strictly adhering to the [REGION_ORDER] (e.g., deploying to a small 'canary' region like `ap-southeast-2` before blasting `us-east-1`). Implement a rigid 'Regional Canary' stage. You must programmatically define the exact [ROLLBACK_CRITERIA], wiring the pipeline directly to specific CloudWatch Alarms so that if a catastrophic error rate is detected in *any* single region during the bake period, the pipeline automatically aborts and violently reverts the infrastructure changes across *all* regions globally. Detail the exact mechanism for securely synchronizing and injecting region-specific environment variables and KMS-encrypted secrets during the build phase.