I would indeed use WRAPPER here instead of rolling my own:

use Template;

my $tt = Template->new;
$tt->process(\*DATA, {
    comp => { name => 'foo', modtime => scalar(localtime) }
}) || die $tt->error();


__DATA__
[% WRAPPER wrap comp = comp %]
content goes here
[% END %]

[% BLOCK wrap %]
<!-- BEGIN  [% comp.name %] ([% comp.modtime %]) -->
[% content %]
<!-- END  [% comp.name %] -->
[% END %]
[download]

Not that this information solves your problem, but HTML::Mason has an autohandler, which not only acts as a WRAPPER, but also gives you finer control at the directory lever: all Mason components in a directory are handled by the autohandler -- and can be used to wrap all components automagically. I haven't found how to do this in TT yet, but i would be surprised if you can't. Hopefully another monk will know the answer, have you tried the TT mailing list?

Update: Herkum++ (that's what i get for getting pulled away from the problem and not refreshing to see if anyone had answered the question :P)

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)