This module converts input text to a PNG image of a QR code containing the
text. The PNG image can either be stored to a file or it can be a scalar.

Image::PNG::Libpng requires "libpng" to be installed. "libpng" should
already be installed on most Linux and Windows systems.

This example makes a data URL QR code:

use Image::PNG::QRCode 'qrpng';
use URI;
my $data = 'abcdefghijklmnopqrstuvwxyz';
my $u = URI->new ('data:');
$u->media_type ('image/png');
$u->data (qrpng (text => $data));
print "<img src='$u'>\n";
