$ perl -e " return "
Can't return outside a subroutine at -e line 1.

$ perl -Mdiagnostics -e " return "
Can't return outside a subroutine at -e line 1 (#1)
    (F) The return statement was executed in mainline code, that is, where
    there was no subroutine call to return out of.  See perlsub.

Uncaught exception from user code:
        Can't return outside a subroutine at -e line 1.
 at -e line 1.