I use eval, $@ and Test::More::like() in my CPAN modules. Here is a snippet from one of my tests:

# Check error messages

$@ = '';
eval { my $str = format_eng() };
like($@, qr/requires numeric input/, 'die if no input');

$@ = '';
eval { my $str = format_eng(' ') };
like($@, qr/not numeric/, 'die if input only has whitespace');
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