Hi Popcorn Dave,

From reading through this thread I thought it was important to make a distinction. Since Tk is event driven you need to specify an event during which your variable is read. One way of doing this is using a polling function. This example displays the contents of $var every second:

#! /usr/local/bin/perl -w
use strict;
use Tk;

my $var  = '';
my $w = new MainWindow;
$w->Entry( -textvariable => \$var )->pack;
$w->repeat(1000, [ \&print_var, \$var ] );

MainLoop;

sub print_var
{
    my $var = shift;
    print scalar(localtime)," >$$var\n";
}
[download]

This is somewhat inelegant because it is called no matter whether your variable has changed or not.

Another thing you may want to play with (I've not had much luck with it) is to use the validate option on your entry widget.

#! /usr/local/bin/perl -w
use strict;
use Tk;

my $var2 = '';
my $w = new MainWindow;
$w->Entry( -validate => 'all', -validatecommand => [ \&print_var, \$va
+r2 ], -textvariable => \$var2 )->pack;

MainLoop;

sub print_var
{
    my $var = shift;
    print scalar(localtime)," >$$var\n";
}
[download]

This basically says that with any action that affects the entry widget perform the validation callback.

Update: I almost forgot to mention - it may be imperitive that you pass a reference to your callback subroutine, particularly with after or repeat. Otherwise they will print out your initial value forever.

Good luck, I hope this helps.
{NULE}
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