The -l switch (that’s the letter ell, for launch, not the numeral one) forces PolyShell to automatically launch the first instance of A-Shell, so that launching PolyShell has the same effect (for an unknowing user) as launching A-Shell. Otherwise, PolyShell starts at its own command menu, from which you can then launch instances of A-Shell. This switch also has the effect of automatically shutting down PolyShell when the last A-Shell child instance is closed. (Otherwise, closing the last A-Shell child instance just returns you to the PolyShell menu, where you can then issue a command to exit entirely or to open up an new child instance.)