Have a look at the -warp portion of eventGenerate. Here's a short example that warps the pointer from a button down to a label when you click the button.

#!/usr/bin/perl
use Tk;
$m=Tk::MainWindow->new();
# create a button with a callback to do_warp
$b=$m->Button(-text => "Press Me", -command => \&do_warp);
# some filler labels so that the pointer warp is obvious
$filler1=$m->Label(-text => "           ");
$filler2=$m->Label(-text => "           ");
# this label is where the mouse pointer ends up
$l=$m->Label(-text => "Mouse ends up here");
$b->pack();
$filler1->pack();
$filler2->pack();
$l->pack();
MainLoop;
sub do_warp {
    $l->eventGenerate('<ButtonPress>',-warp => 1);
}
[download]

Update: I should probably mention that moving the pointer around is generally considered "bad juju", and not the best UI design.

Thanx a zillion already. I know it's bad use in UI design, but in my case it's for a speech-application for disabled, non-speaking people. They have only limited possibilities to operate a mouse, and with a special device and special buttons they still can operate it. What I want to prevent is that accidentally the application loses focus, because they cannot correct that.

But can I also 'warp' the mousepointer on a mouse-motion event? I tried that, and could not get it to work.

Jouke Visser, Perl 'Adept'

Here's an example that keeps the pointer locked inside a label widget. Hopefully this is closer to what you were asking for. You'll have to fill in getting the x/y coordinates for the event from Tk::bind and warping the pointer to a sensible spot

You may also want to have a look at Tk::grab. You can maintain the focus for keyboard traversal without confining the pointer, if this is useful.

Familiarize yourself with keyboard control of focus before you run this :)

#!/usr/bin/perl
use Tk;
use strict;
my $m=Tk::MainWindow->new();
# create a big label so that the window is large
# enough to demonstrate this
my $label=$m->Label(-bd => 5, -relief => "ridge",
         -text => "Label Text Here\n" x 10)->pack();
#
# bind Leave events from the label to 
# generate a useless virtual
# event. 
# (We don't really need to fire an event
# , we just need the warp option)
# Without the -x/-y options, it warps 
# the pointer to the nw corner of the widget
#
$label->bind('<Leave>', sub { 
           my($w)=shift;
           $w->eventGenerate('<<Not Used>>', -warp => 1);
       }
);
MainLoop;
[download]