Your problem is a common one, in all gui toolkits, it's called "blocking the event loop". All gui's use an event loop, that is why they can be responsive to button clicks, etc. When you put a sleep statement, or do something which is long and intensive like getting a url thru a slow netlink, the event loop will freeze until it regains control. This can be shown is the following example. After 2.5 seconds, it will freeze for 5 seconds 
#!/usr/bin/perl
use Tk;

my $mw = MainWindow->new;
$mw->geometry('100x100+100+100');
#$mw->overrideredirect(1);

my @color = qw/red green/;

my $bits = pack("b8"x8,
"...11...",
"..1111..",
".111111.",
"11111111",
"11111111",
".111111.",
"..1111..",
"...11...",);

$mw->DefineBitmap('indicator' => 8,8, $bits);

my $label = $mw->Label(
              -bitmap=>'indicator', 
          -bg=>'black',
          -fg=>'red',
          )->pack;

$mw->repeat(500,sub{$label->configure(
                               -fg=>$color[0]);
                               @color=reverse(@color);
 });


# put in simulated eventloop blocker after 2.5 seconds
# to freeze tk for 5 seconds
$mw->after(2500,sub{ sleep (5)  });

MainLoop;

[download]
There are many ways around this problem. First never use sleep in a gui app, unless it's in a thread. Second, put your url_fetching operations into threads or fork them off. You can try to manually pump the loop by liberally sprinkingly DoOneEvent(); in areas where the code is in a delay loop( like your in while( $fh ). Finally, use Tk::fileevent to read your filehandles, instead of a while loop. Use timers when needing delays, like Tk::repeat.

There are many examples out there on google for using Tk with threads and shared variables. See Tk events by Lidie and a few examples of using threads and fileno's with Tk ztk-BBC-World-News-Rss-TickerTape and Re^3: Passing globs between threads

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku

In reply to Re^3: Perl Tk freezes when command button is clicked ! by zentara
in thread Perl Tk freezes when command button is clicked ! by muralidharan

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