Let me guess. You saw how to use Term::ReadKey in perldoc perlfaq8 and it told you to:

use Term::ReadKey;
ReadMode('noecho');
$password = ReadLine(0);
[download]

But you did not pay attention to the line above it...
You can also do this for most systems using the Term::ReadKey module from CPAN, which is easier to use and in theory more portable.

Have you tried installing the CPAN module Term::ReadKey? It is not hard.