How to set variables with multi values in GitLab CI/CD?

I am trying to edit yaml file to construct ci/cd in a gitlab project, troubled with the variables problem. I set a variable whose value is file path, and the number of file paths is multiple, so that I can use the words rules: changes: '$var'. But how can I set the variables with multi values? If I use the wildcards, just like this: variables: COMMON_FILE: ./{ci/*,camke/*,*.yml}, Then use rules: changes: '$COMMON_FILE' in the job, it will cause such error:"Local file'./ci/*' does not exist". If I reduce the number of file path, like this: COMMON_FILE: ./ci/*, it will not work yet. If the variable is like this: variables: COMMON_FILE: ci/*, it's ok. It seems that a file path with the prefix './' will not work. If I don't use wildcards, I must set more variables. Thus, is there any way that a variable could have multi values in the yaml file of gitlab ci/cd?