I'd say, especially if your menu will contain mostly the same stuff except for the label text, you should definately re-use the popup menu. Update: Though, if your menus are going to be completely different depending on where the user clicked, it would probably make more sense to pre-generate all the menus. Unless you have a lot of them. I guess, uh, it just depends. ;-)

As for how to tell what label was under the mouse, just use the 'W' parameter to Ev(), like so:

# this is all documented under Tk::bind
$mw->bind('<3>', [\&callback, Ev('X'), Ev('Y'), Ev('W')]);
[download]

...and it should pass you a reference to the widget that was clicked upon (as the fourth parameter).

Update: Oh, and, uh, you'd have to alter the menu within the callback that shows it (just before posting) because I don't know of an easy way to pass an argument (ie, the clicked widget) to the postcommand() method.

Update2: Uh, like this: :-)

#!/usr/bin/perl

use Tk;
use Tk::Menu;

$mw = MainWindow->new();

$menu = $mw->Menu(-tearoff => 0);
$menu->add('separator');
$menu->add('command', -label => 'One', -command => \&item1);
$menu->add('command', -label => 'Two', -command => \&item2);

$mw->Label(-text => 'Label 1')->pack();
$mw->Label(-text => 'Label 2')->pack();
$mw->Label(-text => 'Label 3')->pack();

$mw->bind('<3>', [\&showmenu, Ev('X'), Ev('Y'), Ev('W')]);
$mw->focus();
MainLoop;

sub showmenu {
  my ($self, $x, $y, $widget) = @_;
  my $label = $widget->cget('text');
  $menu->insert(0, 'command',
    -label => $label,
    -command => sub { print "Clicked $label.\n" },
  );
  $menu->post($x, $y);
  $menu->delete(0,0);
}

sub item1 { print "Item 1!\n" }
sub item2 { print "Item 2!\n" }
[download]

bbfu
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Nor do the wind, the sun, and the rain.
We can be like they are.