use HTML::Template;
my $t = HTML::Template->new(
    scalarref => \'[%!-- TMPL_VAR name="foobery" escape=html --%]',
    filter => sub {
        my $text_ref = shift;
        $$text_ref =~ s|
            \[\%
            (?:!--\s*)? # 
            (
                [Tt][Mm][Pp][Ll]_
                [^\]]+?
            )               #$1
            (?:--\s*)?
            \%\]
        |<$1>|xg;
    }
);

$t->param(foobery => 'barbery>>');
die $t->output();
__END__
barbery&gt;&gt; at html.template.pl line 11.