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

##</code><code>##

my $magic = sub {
    my $textref = shift;
    # note the extra $ on the $textref var
    $$textref =~ s/!!!blargle!!!/<tmpl_include $policy_file>/g;
};