-- | Reads the current value of the environment variable.
-- If it no longer exists, a run time error will occur.
runEnvVar :: EnvVar -> Experiment String
runEnvVar (EnvVar v) = liftIO $ getEnv v
runEnvVar :: EnvVar -> Experiment String
runEnvVar (EnvVar v) = liftIO $ getEnv v
runEnvVar (EnvVar v) = liftIO $ getEnv v