Pattern Matching with Variables Causes GitLabs CI Lint to Throw 500

Summary

Pattern Matching in .gitlab-ci.yml file with Variables Causes GitLabs CI Lint to throw 500.

Also, pipelines fail with invalid yaml error.

Steps to reproduce

See this documentation: https://docs.gitlab.com/ee/ci/variables/#supported-syntax

According to documentation this logic works: $VARIABLE_1 == $VARIABLE_2

and this works as well: $VARIABLE =~ /^content.*/

But if you use use a combination of the two like $VARIABLE_1 =~ $VARIABLE_2 it causes errors and pipeline failures.

Example Project

This works:

---
variables:
  DEVELOP_BRANCH_REGEX: /^develop/

stages:
  - test

test:good:
  stage: test
  only:
    refs:
      - branches
    variables:
      - $CI_COMMIT_REF_NAME =~ "/^develop/"
  script:
    - 'echo $CI_COMMIT_REF_NAME'

But DOES NOT work:

---
variables:
  DEVELOP_BRANCH_REGEX: /^develop/

stages:
  - test

test:exception:
  stage: test
  only:
    refs:
      - branches
    variables:
      - $CI_COMMIT_REF_NAME =~ $DEVELOP_BRANCH_REGEX
  script:
    - 'echo $CI_COMMIT_REF_NAME'

What is the current bug behavior?

GitLabs CI Lint page throws 500 error.

Pipelines fail with invalid yaml error.

What is the expected correct behavior?

Pattern matching with two variables to work correctly.