I'm not quite sure about what you mean, but you might be looking for the -show attribute of Tk::Entry. Example:

#!perl -w
use strict;

use Tk;

my $main = new MainWindow;

my $entry = $main->Entry(-show => '*')->pack;

MainLoop;
[download]

Hope this helped.
CombatSquirrel.

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Entropy is the tendency of everything going to hell.