Hello! Welcome to the PerlMonks - you've come to the right place.

1. You don't need to include <br> inside <code> tag.
2. Parsing part is so crappy :) But don't worry - I used it too :)

Here is classic hello world script that will become your best friend from now on ...

#!perl

use strict; # this is a MUST!
use CGI; # so you don't parse it by hand

my $query = CGI->new(); # my is because of strict pragma

print $query->header(); # so you don't do it by hand

print "Hello World!";
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When you have something like that (inside $query you have an CGI object) you can easily get any post or get parameter passed to your script easily.

my $form = $query->Vars();
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In this case, $form will contain a hashref of form fields. So if you want to say print value of field called "name" :

print $form->{name};
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Now let's address your Show_Critical_Error() function :)

Add this to top of your script.

use CGI::Carp qw(fatalsToBrowser);
....
....
if($error) { die "Error message"; }
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And it will print a relatively nice error message to the browser ;)

I believe this is enough to get you started! There are many more things to learn, but take them one by one ...