#!/usr/bin/perl

use strict;
use warnings;

open my $fh, '>', 'demo.txt' or die $!;

print $fh "Content-type: text/html\n\n";

foreach my $key (sort keys %ENV) {
    print $fh "\$ENV{$key} = $ENV{$key}<br />\n";
}

close $fh or die $!;