Problem with signal_connect

[Rosalind Mitchell <info swimbarrow co uk>]

I recently upgraded to the lastest version of Kubuntu.

Since then I have been playing around with Gtk-based applications in Perl.  
However, where I could do this fine before, even a simple example like

#!/usr/bin/perl -w

use strict;
use Gtk2 '-init';

my $mwin = Gtk2::Window->new( 'toplevel' );
$mwin->signal_connect( destroy => sub { Gtk2->main_quit } );

$mwin->show;

Gtk2->main;

generates the error message

Can't locate object method "signal_connect" via package "Gtk2::Window" 
at ./test-gtk line 7.

Any bright ideas?  Running under Kubuntu 6.10

Rosie