sub path_to_op
{
    my ( $root, $tgt ) = @_;

    local $op = $root;
    local @path;

    '' =~
        /(?:
            (?(?{ my $name = $op->oldname;
                  local $op = $op->parent;
                  local @path = ( @path, "$name/" ); })(?=)|(?!))
            |
            (?(?{ my $name = $op->oldname;
                  local $op = $op->sibling;
                  local @path = ( @path, "...," ); })(?=)|(?!))
         ) *

         (?(?{ $$op == $$tgt })(?=)|(?!)) /x;

    @path;
}