In the conda environment.yml file, how do I append to existing variables without overriding them?

This is a follow up question for this answer. For a conda environment specification file environment.yml, if the variable that I am defining is PATH, for example, how can I prepend or append to it instead of just overwriting it? Is the following correct?

name: foo
channels:
  - defaults
dependencies:
  - python
variables:
  MY_VAR: something
  OTHER_VAR: ohhhhya
  PATH: /some/path:$PATH

from In the conda environment.yml file, how do I append to existing variables without overriding them?