eval { print speak('sheep'), "\n"; };
print $@ if $@;

my %says = (
    sheep  => 'baa',
    monkey => 'foo',
);

eval { print speak('monkey'), "\n"; };
print $@ if $@;

sub speak {
    my $animal = shift;
    die unless defined $says{$animal};
    return $says{$animal};
}
__END__
Died at Perl-1.pl line 21.
foo