How to access environment variable in BPMN file

I have use case. I have created service task for SOURCE connector and we are sending the kafka-topic as header. Kafka-topic value contain environment suffix. For example, save-content-to-s3-{ENV}.
ENV values are dev,test,stage,prod.
I am using zbctl command line tool to deploy the BPMN. Currently, I have create four BPMN file with hard coded kafka-topic.
I also tried below as value “save-content-to-s3-”+java.lang.System.getenv(‘ZEEBE_ENV’). But this is not working. I just wanted to create single BPMN file.
I have added ZEEBE_ENV variable in helm chart dev value file as below.

clusterSize: “3”
partitionCount: “12”
replicationFactor: “2”
cpuThreadCount: “12”
ioThreadCount: “12”
pvcSize: “100Gi”
pvcAccessModes: [ “ReadWriteOnce” ]
env:

  • name: ZEEBE_BROKER_BACKPRESSURE_ENABLED
    value: “true”
  • name: ZEEBE_BROKER_BACKPRESSURE_ALGORITHM
    value: “vegas”
  • name: ZEEBE_BROKER_BACKPRESSURE_FIXEDLIMIT_LIMIT
    value: “100”
  • name: ZEEBE_ENV
    value: “dev”