---
- hosts: "{{ env }}_web"
  remote_user: myuser

[dev_web]
217.0.10.8

[stage_web]
217.0.10.9

[prod_web]
217.0.10.10

ansible-playbook "-e env=staging" playbook.yml (works as expected)

tower-cli job launch -J 46 --extra-vars env='dev' --monitor

ERROR! The field 'hosts' has an invalid value, which includes an undefined variable. The error was: 'env' is undefined