Template::Toolkit (TT) is the most powerful templating language in Perl; well, maybe it’s really Mason, but that is a digression. It’s not necessarily a good thing.
My POV: I love and use Template and have for 15ish years. I don’t use it for new projects. It is complex enough that it becomes a mini-language, so you’re not really doing Perl and you’re not really handing off templates to designers or non-coders that they will be able to understand and edit. It can easily make a clean MVC design into spaghetti soup by embedding all three elements in templates.
Also TT is extremely slow compared to something like Text::Xslate. Xslate has the benefit of being a more pure View. It’s got a few affordances but it doesn’t really rise to the level of mini-language. If you’re using Mojo, its templates might be a better idea than TT.
The only clear advantage I see in learning TT is that many legacy projects use it, so it might be nice to know when job hunting.