Double quoted strings cause variables to be interpolated; they don't cause code to be executed.¹ $template->output is a method call. The variable, $template is interpolated into the string. Stringified, it looks like "HTML::Template=HASH(0x814a750)" which indicates that it is a hash reference which has been blessed as an HTML::Template. In other words, it's an HTML::Template object. The "->output" portion of that string is printed literally.

So, to fix the problem, remove the double quotes (as LTJake suggested.)

1. Yes, there are ways to get double quoted strings to execute code but that takes some trickery.

-sauoq
"My two cents aren't worth a dime.";