I'm searching fo guidance on add a feature to my recent Tk sparetime project. My probably naif understanding of the MainLoop is the mother of all errors. I'm seeking, if possible, explaination and examples.

Problem: I want to add an autoplay function to a secondary TopLevel window. In the below, semplified, example I display a sequence of chars A..Z A button on the primary window starts the autoplay function, and this works in the way I expected. But it turns out I'm not able to stop that autoplay. I imagined that checking a $toggle_autoplay variable was sufficient. I've bound the variable to the p key on the keyboard. It seems though that the variable remains unchanged (UPDATE: it seems the problem was an if?then:else related problem. the longer contruct below works...).

A)Is this the best way to implement an autoplay function? I tried to use Tk's repeat and timer with no big success. I read all tk callback material but if I understood it correctly a variable used in the callback it is evaluated when the callback is created NOT when it is invoked. How to change this behaviour?

B)why the ' ? : ' construct fails? Why it only works with an if(){}else{} one. Are not the same?

Background: the real application shows photos on the secondary window. I dont want to use modules like Tk::Slideshow or similar to accomplish the task. I want to do it on my own to understand better how MainLoop works.

The below code shows what i'm working on ()

#!/usr/bin/perl
use warnings;
use strict;

use Tk;
use Tk::Pane;
use Tk qw(:eventtypes);

my $mw = new MainWindow (-title=>" $0 MAIN");
my $phwin;
my $display_label;
my @to_show =('A'..'Z');

my $toggle_autoplay = 0;

my $fr0 = $mw->Frame()->pack();

$fr0->Button(  -text => "autoplay",
               -command =>  sub{$toggle_autoplay = 1; &autoplay},
               #[\&autoplay, Ev $toggle_autoplay?$toggle_autoplay=0:$t
+oggle_autoplay=1],
      )->pack();
# ok same behaviour of ->update
#$mw->DoOneEvent(DONT_WAIT | ALL_EVENTS);#
# the above without bitmask run but not at the right interval
#also ok is:
$mw->update;
&secondary_win;
MainLoop;

######################################################################
+##########
sub autoplay {
       while($toggle_autoplay){

            $display_label->configure(-text=> shift @to_show);
            $phwin->update;
            #$phwin->DoOneEvent;
            sleep 1;
            #last if $phwin->waitVariable(\$toggle_autoplay);
       }
}
######################################################################
+##########
sub secondary_win {
    # window does not exists
    if (! Exists($phwin)) {
      $phwin = $mw->Toplevel();
      $phwin->title("SECONDARY");
      $phwin->bind('<KeyRelease-p>' => sub {
                                            print "BEFORE: bind-p = $t
+oggle_autoplay\n";
                                            # THIS WORKS
                                            #if ($toggle_autoplay == 0
+){
                                            #   $toggle_autoplay = 1;
                                            #}
                                            #else{
                                            #    $toggle_autoplay = 0;
                                            #}
                                            # THE FOLLOWING DOES NOT W
+ORKS! WHY?
                                            $toggle_autoplay == 0 ?
                                            $toggle_autoplay = 1  :
                                            $toggle_autoplay = 0  ;
                                            print "AFTER: bind-p = $to
+ggle_autoplay\n";
      })
    }
    # window Exists
    else {
      $phwin->deiconify( ) if $phwin->state() eq 'iconic';
      $phwin->raise( ) if $phwin->state() eq 'withdrawn';
    }
    #my $scrolledframe = $phwin->Scrolled('Frame',-scrollbars => 'osoe
+')->pack();

    $display_label = $phwin->Label(-text=>'SECONDARY')->pack;
}
[download]

Thanks in advance!

L*