I don't quite understand. I have updated the code (to the best of my ability) to use the CGI module. Perhaps, I am leaving something out. Keep in mind that the actual script will accept any number of parameters through an HTML form.

#!C:\Perl\bin\perl.exe

use strict;
use warnings;
use CGI;

my $req_meth = CGI->request_method();

sub readPostInput() {
    my (%searchField, $buffer, $pair, @pairs);
    if ($req_meth eq 'POST')
    {
        read (STDIN,$buffer,$ENV{'CONTENT_LENGTH'});
        @pairs = split(/&/, $buffer);
        foreach $pair (@pairs)
        {
            my ($name, $value) = split(/=/, $pair);
            $value =~ tr/+/ /;
            $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/e
+g;
            $name =~ tr/+/ /;
            $name =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg
+;
            $searchField{ $name } = $value;
        }
    }
}

my %postInputs = readPostInput();

print "Content-type: text/html\n\n";
print "Complete :: $req_meth";
[download]

After these changes I still receive the same error.