This has nothing to do with CGI or Perl, and seems to me to only relate to HTML and hyperlinking.

To my knowledge, neither HTML or the URIs used by HTML allow you to create a link to something that does not have a <a name="foo"> anchor to it. You can link to the top of a page by not using an URI anchor and you can link to a named part of the page by using the name of the respective anchor, but further granularity is not possible.

If you want to show highlighted or annotated parts of a webpage, your program will need to create a link to itself and then at display time, download the real page and serve up a highlighted version of it.