(alias
 (name echo1)
 (action (echo %{env:DUNE_ENV_VAR=true})))

(alias
 (name echo2)
 (action
  (progn
   (echo "previous env: %{env:DUNE_ENV_VAR=unset}\n")
   (setenv DUNE_ENV_VAR "set by setenv"
    (echo "new env:%{env:DUNE_ENV_VAR=unset-by-env}")))))

(alias
 (name enabled)
 (enabled_if (= true %{env:DUNE_ENV_VAR=true}))
 (action (echo "enabled!")))

(alias
 (name disabled)
 (enabled_if (= true %{env:DUNE_ENV_VAR=false}))
 (action (echo "enabled!")))
