Straying a little more off topic...

I'll second the recommendation of using something like prototype.js for this. Your xmlHTTPRequest will look like this:

   new Ajax.Request( '/url/to/post/to',
   { asynchronous: true,
     evalScripts: true,
     parameters: Form.serialize(this),
     onComplete: jsFunctionToCallBack
   });
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If you're using Catalyst (ah, back to perl!) there's even a handy Prototype plugin to make things a little easier.

Recently, though, I've been turned onto jquery which is a little more lightweight than prototype, and much better documented. The above post would then look something like:

    $.ajax( {
              url: '/url/to/post/to',
              type: 'POST',
              dataType: 'html',
              data: $('form#form_id').formSerialize(),
              complete: jsFunctionToCallBack
            }
          );
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s**lil*;  $*=join'',sort split q**;  s;.*;grr; &&s+(.(.)).+$2$1+; $; =
qq-$_-;s,.*,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$*,$/)
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