Like this:

#!/C:/perl/bin/perl

use strict;
use warnings;

use MIME::Lite;
use Data::Dumper;

my $msg = MIME::Lite->new(
              Type     =>'image/png',
              Encoding =>'base64',
              Path     =>'test.png'
              );
my $str = $msg->as_string;
print $str;
[download]

Did you even bother to try anything?