rkrasowski has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, I know this is very basic question, but I am loosing my mind trying to solve it. Task is very simple, I am trying to create simple application to read data from serial port. The problem I have is Tk. I created nice window but I can not find out how to update textvariable for particular labels. Here is a simple example of code that should display current Unixtime, but does not, what is the problem?? 
#!/usr/bin/perl 
use warnings;
use strict;

use Tk;



my $mw =  new MainWindow;
my $label = $mw -> Label(-textvariable =>\&timer);
$label -> grid(-row=>1,-column=>1);

$mw->repeat(1000,\&timer);


MainLoop;

sub timer{
    my $time = time();
}

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Re: Tk and textvariable update
by GrandFather (Saint) on Dec 19, 2011 at 01:13 UTC

    The main problem is that you aren't using a variable for -textvariable for the label. The code below fixes that and also passes a reference to the variable through to the sub that updates its contents:

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

use Tk;


my $mw = new MainWindow;
my $time;
my $label = $mw->Label(-textvariable => \$time);
$label->grid(-row => 1, -column => 1);

$mw->repeat(1000, sub {timer (\$time)});

MainLoop;


sub timer {
    my ($varRef) = @_;
    
    $$varRef = time();
}

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    True laziness is hard work
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Re: Tk and textvariable update
by ~~David~~ (Hermit) on Dec 19, 2011 at 06:19 UTC
    Another way: 
    #!/usr/bin/perl 
use warnings;
use strict;

use Tk;

my $mw = new MainWindow;
my $time = time();
my $label = $mw->Label(-textvariable => \$time);
   $label->grid(-row => 1, -column => 1);

$mw->repeat(1000, sub{ $time = time(); } );

MainLoop;

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