Capturing and Testing Warnings (1)

• Sometimes a newly visible warning is significant ...

  • ... significant enough that we want to verify that it was emitted

• From: t/uni/readline.t in blead

        use constant roref=>\2;
        eval { for (roref) { $_ = <Fʜ> } };
        like($@, qr/Modification of a read-only value attempted/, '[perl #19566]');