Is this a CGI or a CLI script?

If the former, then then you can just use a password field. From the CGI docs:

       CREATING A PASSWORD FIELD

          print $query->password_field(-name=>'secret',
                                       -value=>'starting value',
                                       -size=>50,
                                       -maxlength=>80);
               -or-

          print $query->password_field('secret','starting value',50,80
+);

       password_field() is identical to textfield(), except that its c
+ontents will be starred out on the web page.
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If it's a CLI script (and you can't/wont use an external module), then you can just put the terminal into "no echo" mode with a system call to stty. The following example is from perldoc perlfunc:

                   system "stty -echo";
                   print "Password: ";
                   chomp($word = <STDIN>);
                   print "\n";
                   system "stty echo";
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For a more portable solution, you'll need to use Term::ReadKey

Cheers,
Darren