Excellent and slick. But one comment: You have excessive backwhackitude. Try

my $oxml = qq(<?xml version="1.0" standalone="yes"?> <data image="$enc
+oded"/>\n);
[download]

Or even

my $oxml = <<EOF;
<?xml version="1.0" standalone="yes"?>
<data image="$encoded"/>
EOF
[download]