give an example of env var substitution
give an example of env var substitution

yvvq/config,wmudge/config,Applied-Duality/config,melrief/config,chris-martin/hocon-python,yvvq/config,cprice404/config,typesafehub/config,malexandert/config,leakingtapan/config,twitter-forks/config,fpringvaldsen/config,jasonchaffee/config,shrutig/config,zeq9069/config,typesafehub/config,rmuhamedgaliev/config,twitter-forks/config,leakingtapan/config,melrief/config,zeq9069/config,meln1k/config,Applied-Duality/config,roznalex/config,meln1k/config,cprice404/config,wmudge/config,malexandert/config,roznalex/config,jasonchaffee/config,chris-martin/hocon-python,rmuhamedgaliev/config,fpringvaldsen/config,shrutig/config