I had to Ctrl-J also. You need a way to get out if necessary. What if the user had second thoughts about putting his password out there, and wanted to quit?

exit 0 if $key eq 'q';
[download]

Here's what I tried:

#!/usr/bin/perl -slw

use strict;
use Term::ReadKey;

my $key = 0;
my $password = "";

print "\nPlease input your password: ";

ReadMode(4);
while(ord($key = ReadKey(0)) != 10) {
    exit 0 if $key eq 'q';
    if(ord($key) == 127 or ord($key) == 8) {
        chop($password);
        print "\b \b";
    } 
    elsif(ord($key) < 32) {
        ();
    } 
    else {
        $password = $password . $key;
        print ord($key);
    }
}
ReadMode(0);
print "\n\nYour super secret password is: $password";
[download]

Update: If 'q' is a problem for you, substitute a fake password like 'quit', 'exit', 'bye', etc. for 'q';