use strict;
use warnings;
use Tk;
use Tk::Canvas;

my ( $X, $Y, $dx, $dy);


my $mw = MainWindow->new(-width => 500, -height => 500);

my $canvas = $mw->Canvas(-width => 500, -height => 500)->place( -x => 0, -y => 0);

my $Button1 = $canvas->Button( -text => "Test" )->place( -x => 10, -y => 40, -height => 24, -width => 150);
$canvas->Tk::bind( '<ButtonPress-1>', sub { startmove(); } );
$canvas->Tk::bind( '<ButtonRelease-1>', sub { endmove(); } );

MainLoop;

sub startmove {
  my $ev = $canvas->XEvent;
  ( $X, $Y ) = ( $ev->x, $ev->y );
  $mw->Tk::bind( '<B1-Motion>', \&moveit );
  }

sub moveit {
  my $ev = $canvas->XEvent;
  my ( $cx, $cy ) = ( $ev->x, $ev->y );
  ( $dx, $dy ) = ( $cx - $X, $cy - $Y );
  my %coords = $Button1->placeInfo;
  $Button1->placeConfigure(-x => ($coords{-x}+$dx), -y => ($coords{-y}+$dy));
  ( $X, $Y ) = ( $cx, $cy );
}

sub endmove {
  my $ev = $canvas->XEvent;
  my ( $cx, $cy ) = ( $ev->x, $ev->y );
  ( $dx, $dy ) = ( $cx - $X, $cy - $Y );
  my %coords = $Button1->placeInfo;
  $Button1->placeConfigure(-x => ($coords{-x}+$dx), -y => ($coords{-y}+$dy));
}