# aptitude install libexpat-dev libgd2-dev
# cpan install GD
# cpan install GD::Barcode::QRcode

#!/usr/bin/perl
use strict;
use GD::Barcode::QRcode;

my $str         = $ENV{'HTTP_REFERER'};
my $header      = qq(Content-Type: image/png\n\n);
my $qr          = GD::Barcode::QRcode->new($str,{ ECC => 'L', Version => 2, ModuleSize =>2,})->plot->png;
print $header,$qr;
exit;

<img src="path/to/qr.cgi" width="97" height="97" alt="QRcode" />