How can I call backticks without shell processing?

This is a bit tricky. Instead of writing 

    @ok = `grep @opts '$search_string' @filenames`;

You have to do this: 

    my @ok = ();
    if (open(GREP, "-|")) {
        while (<GREP>) {
	    chomp;
            push(@ok, $_);
        }
	close GREP;
    } else {
        exec 'grep', @opts, $search_string, @filenames;
    }

Just as with system, when you exec a list, so no shell escapes happen.