...
use Scalar::Util;
use Glib qw(TRUE FALSE);
...

sub _init {

...

# Creating the "Ok"-button
$button_ok = Gtk2::ToolButton->new( undef, 'Ok' );
$self->{ButtonOk} = $button_ok;

# Connecting the signal-handler to it
$button_ok->signal_connect( 'clicked' => sub { $self->_ok_pressed( @_ ) } );

}

# The signal handler
sub _ok_pressed {
   
   my ( $self, $button, $event ) = @_;
   
   # Make button and event object properties to have them available outside the
   # signal handler's scope
   $self->{EventHash}->{Button} = $button;
   $self->{EventHash}->{Event}  = $event;
   
   # Clear the summary, navigate to other notebook page
   ...
   
}

# The _save_work subroutine
sub _save_work {

   # Parameter processing, declarations, etc.
   ...

   # The actual loop which waits for the event
   while ( TRUE ) {
         
         # Give the main loop the chance to intercept events with the program
         # being in this loop
         while ( Gtk2->events_pending() ) {

            Gtk2->main_iteration();
            
         }
         
         if ( %{$self->{EventHash}} ) {
            
	# This checks whether the expected TYPE of event ocurred and whether it 
            # was passed to the expected WIDGET (the "Ok"-button)
            if ( ( refaddr( $self->{EventHash}->{Button} )
                 == refaddr( $self->{ButtonOk} ) )
                 && ( defined( $self->{EventHash}->{Event}->{'type'} ) )
                 && ( $self->{EventHash}->{Event}->{'type'} eq 'button_press' )   
                 && ( $self->{EventHash}->{Event}->{'button'} == 1 ) ) {

              # Code executed after pressing the "Ok"-button goes here
              ...
              $self->{EventHash} = ();
              last; 

             }
                
         }
         
      }

}