$str = "<story>
                <page>
                        <description> desc </description>
                        <image> notExpected.jpg </image>
                        <headline> head </headline>
                </page>
        </story>
        <image>correctImage.jpg</image> ";

$str =~ m/[^<story>].*?<image>(.*?)<\/image>.*?[^<\/story>]/s;
print $1;