Where's the magic?
!!!blargle!!! ##
##

#!/usr/bin/perl

use Modern::Perl;
use HTML::Template;

# This is the part that would be context-driven, if it worked...
my $policy_file = 'test-policy.html';

my $magic = sub {
    my $textref = shift;
    $textref =~ s/!!!blargle!!!//g;
};

my $t = HTML::Template->new( 
    filename => '/web/filter/data/magic-tmpl.html', 
    filter => $magic
);

say $t->output;

__END__

Produces:
Where's the magic?
!!!blargle!!!