What you need is some sort of routine that loads your form page, looks for field data insertion points, and adds the data. For instance, instead of:

<input type="text" name="Email" size="20">
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you might have:

<input type="text" name="Email" size="20" value="Email">
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And then a routine might load the page into a variable and perform the following replace (untested, but should theoretically work):

$text =~ s/value="(.*?)"/'value="'.$query->param($1).'"'/eg;
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This will of course not work for textareas, selects, etc., but a slightly more advanced templating system will be able to manage those as well.