If you don't insist STDIN, and open to GUI solution, I stripped piece of my old code, and here it is: (you don't need to port your entire application to GUI, just use this to get password. It can be easily wrapped in a function.)

use Tk;
use Tk::DialogBox;
use strict;
use warnings;

my $mw = MainWindow->new(title => "Password Demo");

my $login_first_try = 1;    
my $id;
my $passwd;

while (1) {
    my $dialog = $mw->DialogBox(-buttons => ["OK", "Cancel"], -title =
+> "Login");
    my $instruction;
    if ($login_first_try) {
        $instruction = "Please provide id/passwd: ";
        $login_first_try = 0;
    } else {
        $instruction = "Failed to login, please try again: "
    }

    $dialog->add("Label", anchor => "w", text => $instruction)->pack(f
+ill => "x");
    my $id_text = $dialog->add("Entry", width => 30)->pack();
    my $passwd_text = $dialog->add("Entry", show => "*", width => 30)-
+>pack();
    $id_text->focus();
    if ($dialog->Show() eq "OK") {
        print "OK pressed, validate here, if okay last and quit the wh
+ile loop"
        #.............
    } else {
        exit;
    }
}
[download]