if (crypt($guess, $pass) eq $pass) {
    # guess is correct
}
*****
$pwd = (getpwuid $<)[1];
$salt = substr $pwd, 0, 2;

system "stty -echo";
print "Password: ";
chop($word = <STDIN>);
print "\n";
system "stty echo";

if (crypt($word, $salt) ne $pwd) {
    die "Sorry...\n";
} else {
    print "ok\n";
}