s{(.*?)(\`([^\']*)\')}
   {$pos += length $1;
    my $length = length $2;
    print ((' ' x ($pos)), "^", (' ' x ($length-2)), "^ ? ");
    my $r = lc <STDIN>; 
    $pos += $length;
    (substr($r,0,1) eq 'n') ? $& : "$1<tt>$3</tt>"
   }eg;