use Gtk2;
use Gtk2::GladeXML;

#This loads description of your GUI, from file named #app.glade
open (GLADE, "<", $sharedir.$execname.'.glade');
my $gladebuf;
while (<GLADE>) { $gladebuf .= $_; }
close (GLADE);
$gladexml = Gtk2::GladeXML->new_from_buffer($gladebuf);

#
# This way you get the object you want to work on:
my $window=$gladexml->get_widget('window');

# There's nothing stopping you from doing this on-the-fly:
$gladexml->get_widget('userName')->set_text($userName);


############
sub on_something_something {
 my $w=$gladexml->get_widget('SomeWidget');
 $w->show_all();
 $w->run();
 $w->hide();
}

# 
Gtk2->main;
exit 0;