Mistakes

$WEB_GID=5001

Much better to use      $WEB_GID = getgrnam("web");


chdir "/web/www.example.com/htdocs";

ALWAYS check the exit status!
At worst, use
           chdir  ...  or die;
           print  ...  or die;
           close  ...  or die;
           chown  ...  or die;
           chmod  ...  or die;