You can use a HTTP::Record to help you to create a Mechanize script, as a like Web Testing with HTTP::Recorder article.

The code bellow do what you want, and don't forget to print to a file, that I didn't.

use WWW::Mechanize;
my $agent = WWW::Mechanize->new();
$agent->get('http://vortex.plymouth.edu/uacalplt-u.html');
$agent->form_number(1);
$agent->field('pt', 'parcel');
$agent->field('mm', '08');
$agent->field('dd', '24');
$agent->field('pl', 'none');
$agent->field('size', '640x480');
$agent->field('yy', '05');
$agent->field('id', 'KMIA');
$agent->field('hh', '00');
$agent->click();

print $agent->{content};
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