This is from Gtk2 code, but should work on Gtk3.

.....
....

 #this will create a treeview, specify $tree_store as its model
 my $tree_view = Gtk2::TreeView->new($tree_store);

  #create a Gtk2::TreeViewColumn to add to $tree_view
  my $tree_column = Gtk2::TreeViewColumn->new();
  $tree_column->set_title ("Select Something");

   #for editing
   my $renderer = Gtk2::CellRendererText->new;
  $renderer->set_property('editable' => TRUE);
  $renderer->signal_connect (edited => \&cell_edited, $tree_store);

.....
.....


sub cell_edited {
  my ($cell, $path_string, $new_text, $model) = @_;

  my $path = Gtk2::TreePath->new_from_string ($path_string);

        my $column = $cell->get_data ("column");
        my $iter = $model->get_iter ($path);

  $model->set_value ($iter, $column, $new_text);

}
[download]