Idea: Restrict block based on JS Referrer

boost serves static html through some .htaccess trickery. Thus when an anonymous visitor is browsing your site, they are getting served a static html file. No PHP is run on the server. I like the Similar by Terms module, but I only want the similar by terms block when the visitor hits it from a search engine that is linking to something other then the frontpage. That's where the JS comes into mind; otherwise you could use some PHP ($_SERVER["HTTP_REFERER"]; $_SERVER['REQUEST_URI'];) and control the displaying of it in the block config. All in all I think it will work, so I need to go write up some JS.

This is the Javascript I'm cooking up, going to wait until later to test on a live site

//lowercase, kill 'http://', kill stuff after '.com/', kill 'www.' if there
var ref = document.referrer.toLowerCase().split('http://').pop().split('.com/').shift().split('www.').pop());
var base = location.href.toLowerCase().split('http://').pop().split('.com/').shift().split('www.').pop());

if (!document.referrer || ref==base) { //no referrer was passed OR referrer is from this website
  $('block-similarterms').hide()
}  
else { //unhide similar by terms div
  $('block-similarterms').show()
}

using boost, so php isn't an option. less then 1% of users to my site have js off, so I'm not worried about it

Here's the working code, just tested it

$(document).ready(function(){
  //lowercase, kill 'http://', kill stuff after first '/', kill 'www.' if there
  var ref = document.referrer.toLowerCase().split('http://').pop().split('/').shift().split('www.').pop();
  var base = location.href.toLowerCase().split('http://').pop().split('/').shift().split('www.').pop();
  //no referrer was passed OR referrer is from this website
  if (!document.referrer || ref==base) {$('div.block-similarterms').hide();}
  //unhide similar by terms div
  else {$('div.block-similarterms').show();}
})

Anyway to add this to the page via a configure option on the admin page? Make it a selection that the admin can choose on admin/settings/similarterms.
http://api.drupal.org/api/function/drupal_add_js

Better yet would be to put the option on the block configure page; that would cause class conflictions though, since the block does not have a unique class. Core theme problem... each block has to have a unique class was never was specified. No good solution, other then to change block.tpl.php :( Guess making it a global option is the best bet for now.

This is missing any configuration options.