Off the top of my head, without looking at how we do it, there is a simple answer.

On the form place a hidden variable, and check for its value with the script. If it's set to value X to action Y. This way a single script can perform multiple functions.

While I'm not saying this is the most efficient code, it does work. (I did bother to look it up)

$CGI = new CGI;
my($item) = $CGI->param('item');
my($add) = $CGI->param('add');
my($sql, $sth, $comments) = ("", "", "");

if(defined($add)) {
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Process the form

} else {
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Show the form