use warnings;
use strict;
use Tk;

my $num = 0;

my $mw = tkinit();
my $button = $mw->Button(
    -text => $num,
    -repeatdelay => 25,
    -repeatinterval => 25,
    -command => sub{
        buttonPressed();
    }
)->pack();
$mw->MainLoop();

sub buttonPressed{
	#this subroutine will be executed if the button is clicked once,
	#or repeatedly executed if the button is held down.
	print ".";
	$button->configure(-text =>	$num++);
}