-- your code goes here
    local mystring='<span class="my-author"><a href="http://aaaa/author/abb-abbb/" title="Posts by abb" class="author" rel="author">abc xyz</a></span>'
    
    local x, y = string.find(mystring,'<span class="my-author">', 0, true)
    local w, z = string.find(mystring,'</a></span>', x, true)
    local author
    print(x,y,w,z)
    if y==nil or w==nil then
        print(author)
    else
        author = string.sub(mystring, y+1, w-1)
                print(author)
    end