Test warnings related to $/
__END__
-w
# warnable code, warnings enabled via command line switch
$/ = \0;
EXPECT
Setting $/ to a reference to zero as a form of slurp is deprecated, treating as undef at - line 3.
########
-w
# warnable code, warnings enabled via command line switch
$/ = \-1;
EXPECT
Setting $/ to a reference to a negative integer as a form of slurp is deprecated, treating as undef at - line 3.