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

my $top = MainWindow->new;
$top->geometry('200x200+200+200');
$top->overrideredirect(1);
$top->Label( -text => 'Click and Drag' )->pack(
    -expand => 1,
    -fill   => 'both'
);

$top->Button(
    -text    => 'Exit',
    -command => sub { $top->destroy }
)->pack;

my @deltaxy;

$top->bind( '<1>' => \&getdelta );

$top->bind( '<B1-Motion>' => \&mousemove );

MainLoop;

sub mousemove {
    my ( $width, $height, $x, $y ) = split /[+x]/, $top->geometry;
    $x = $top->pointerx - $deltaxy[0];
    $y = $top->pointery - $deltaxy[1];
    $top->geometry( $width . 'x' . $height . "+$x+$y" );
}

sub getdelta {
    @deltaxy = ( $top->pointerx - $top->x, $top->pointery - $top->y );
}