Conditional Jobs in CI for use with environments

I want to run a conditional build that is triggered by an api trigger, but only when the ref passed in by the trigger matches a specific regex. I can imagine 2 ways this could be done:

Logical operators in .gitlab-ci.yml's only: directive like so:

only:
   - /^staging-v.*$/ AND triggers

or

Controlling the result status using return codes

script:
   - return 3;

could interpreted as "not run" or "skipped"

This would be handy with the new environments feature of GitLab 8.9.