I like zentara's code more... but here is my rendition of the script you provided converted to perl/Tk... 
use warnings;
use strict;
use Tk;
use Time::HiRes qw(time);

my ($counter,$timerBtn,$resetBtn,$startMoment,$timer);

my $counterText = '0.00';
my $elapsedMS = 0;
my $stopped = 1;
my $mw = tkinit();
$counter = $mw->Label(
    -textvariable => \$counterText,
    -relief       => 'raised',
    -width        => 10,
    -padx         => '2m',
    -pady         => '1m'
  );

$timerBtn = $mw->Button( 
        -text       => 'Start', 
        -command    => sub {
            if ($stopped){
                $stopped = 0;
                $startMoment = time();
                $timerBtn->configure(-text => 'Stop');
                tick();
            } else {
                $timerBtn->configure(-text => 'Start');
                $timer->cancel();
            }
        }
    );

$resetBtn = $mw->Button(
        -text       => 'Reset',
        -command    => sub{
            $startMoment = time();
            $counterText = '0.00';
        }
    );

$counter->pack(-side => 'bottom', -fill => 'both');
$timerBtn->pack(-side => 'left', -fill => 'both', -expand => 'yes');
$resetBtn->pack(-side => 'right', -fill => 'both', -expand => 'yes');

sub tick{
    unless ($stopped){
        $timer = $mw->repeat(50, sub{ counter(); });
    }
}

sub counter{
    $elapsedMS = (time() - $startMoment);
    $counterText = sprintf("%.2f",$elapsedMS);    
}

$mw->bind('<Control-c>', sub{ $mw->destroy() });
$mw->bind('<Control-q>', sub{ $mw->destroy() });
$mw->MainLoop();

[download]

In reply to Re: A timer in Tcl/Tk in Perl::Tk by bcarroll
in thread A timer in Tcl/Tk in Perl::Tk by pashanoid

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