If you go off into a while() like that you will slow down the main loop drastically. How often do you need to check the time? Look at Tk::after in the Tk docs which will tell you how to include a delay loop or a repetitive loop in the Tk mainloop function.

To update the GUI, just use $mw->update(); where $mw is the MainWindow and the GUI elements will update. Put the update in the loop.

jdtoronto

When you program in Tk, you have to change your mindset to think in terms of event-driven programming.

Here's an example of how you could use the Tk "repeat" function, to execute a command every second:

# Create a new main window object called $mw
my $mw = new MainWindow();

# ... other GUI setup here

# Call repeat to execute your subroutine every second (1000 millisecon
+ds)
my $loopStop = 0;    # A pointer to this will be passed to the subrout
+ine
my $hour;            # However this is calculated ...
$mw->repeat(1000 => [ \&CheckTime, \$loopStop, $hour ]);
MainLoop();          # The MainLoop goes last


# And here's the subroutine                                           
+                                
sub CheckTime {
    my ($ploopStop, $hour) = @_;
    $exeTime=18;
    if ($$ploopStop == 0) {
        my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)
            = localtime(time);
                                                                      
+          
        $ZWIDGETS{'Text1'} -> insert('end',"Waiting......\n");
        if ($hour == $exeTime) {
            $ploopStop = 1;
            $ZWIDGETS{'Text1'}->insert('end', "Starting.....\n");
        }
    }
    return $hour;
}
[download]

Note that you don't need to sleep in the subroutine; that would only slow down the entire GUI, as jdtoronto pointed out.

When the value of $hour (however you are calculating it) is equal to $exeTime, the variable pointed to by $ploopStop is set to 1, so on subsequent calls, the logicthe documentation for Tk::repeat to see how to cancel an event loop.

liverpole has answered your question, but there are a few tips that may help you in general.

• Use strictures. Add use strict; use warnings; at the top of every script you write. They will save you time.
• Convince your editor to use spaces for indentation rather than tabs. Your code looks a mess because the tabs have evaporated.
• Avoid putting multiple statements on a line. Unless you are writing on a PDA, screen lines are not generally an issue and putting stuff where it can be seen makes a big difference to understanding - especially when other people may have to work with you code.