The "Use packed template" option is overzealous. It cleans up all whitespace around HTML::Template syntax. For example, if you put this in a template:
<tmpl_if displayTitle>Foo</tmpl_if>Bar
You would expect the result to be "Foo Bar", since that is what you would get from the not-packed template. But when the template is packed, the result is "FooBar", without any whitespace.
This means that packing a template may cause changes for the user. I assume that that's a bug.
If I understand correctly, in this case the \n</tmpl_if>\n is simply removed. But it should be replaced by a single space. This should be fixed for all statements: tmpl_if, tmpl_unless, tmpl_loop, both start and end tags. And for the tmpl_var too.
Found in 7.7.32, confirmed in 7.8.13.
Thanks,
Rogier