I think what Joost is saying is that your example has so many things wrong with it that it's probably better for you to read a CGI tutorial than for someone here to try to explain/correct it. I did a little search and this looks like a good start:

Also, the CGI.pm documentation:

Briefly, though, your two main problems are:
- no actual form input elements in your HTML page (only data in an <input> element will actually get passed to your CGI)
- once you get that sorted out, you can read the values of those fields in your script like so:

$query = new CGI;
my $datefile = $query->param('datefile');
my $datajoin = $query->param('datajoin');
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