Havent tried it, but a quick glance of the links you provided makes it look like what ColdFusion did in 1996. The goal to

support the separation of the HTML presentation from your application logic

is nothing new and ClearSilver (in terms of syntax) does not appear to offer anything innovative, nor anything that cannot already be done with native Perl, or the myriad templating systems available therein.

As far as "language-neutral" ... there is no such thing. That's marketing-speak for "learn a new mini-language on top of the one you are already using". ClearSilver does not appear to offer anything remarkable that isn't already available.