#! @ENV_PROG@ nix-shell
#! nix-shell "{ script, path, ... }: assert path == ./shell.nix; script { }"
#! nix-shell --no-substitute
#! nix-shell --expr 
#! nix-shell --arg script "import ./shell.nix"
#! nix-shell --arg path "./shell.nix"
#! nix-shell -A shellDrv
#! nix-shell -i bash
echo "$FOO"