#!/usr/bin/perl -T
use strict;
use warnings;
use CGI::Pretty qw/:standard/;
my $result=magicFormula();
print header,     
<<END_HTML;
$result
THIS IS WHERE YOUR INITIAL PAGE GOES WITHOUT THE HEAD SECTION
...
END_HTML

sub magicFormula{
   my $_value1=param('value1');
   my $value=($_value=~/^\d+(?:.\d+)?/); # make sure our input is numeric
   # repeat for all values you expect from form in the page above
   my $result=...# PERFORM MAGIC ON INPUT VALUES
   return "<p> The result of running the magic formula on $value1...$valuen is $result</p>
<p>Re-enter the values below to check another </p>" if $result;
}