The problem apparently is that it is being checked if $self->_handle is defined, but then ->opened is being called on $self->io_handle, which is undefined in your case.

    if (defined $self->pathname) {
        $self->io_handle(IO::File->new);
        $self->io_handle->open($self->pathname, @args) 
          or $self->throw($self->open_msg);
    }
    elsif (defined $self->_handle and
           not $self->io_handle->opened   # <-- line 88
          ) {
        # XXX Not tested
        $self->io_handle->fdopen($self->_handle, @args);
    }
[download]

I think that piece of code should be

    ...
    elsif (defined $self->_handle) {
        if ($self->_handle->opened) {  # already open ? --> set/use it
            $self->io_handle($self->_handle);
        } else {                       # not open       --> open it
            # XXX Not tested
            $self->io_handle->fdopen($self->_handle, @args);
        }
    }
[download]

At least that works for me with your test case.  Not sure about the else "XXX Not tested" branch, though... (probably still wrong, because I suppose the ->fdopen() would fail as well (just like ->opened), in case $self->io_handle is undefined).