if ((!($username eq 'sugar'))  && (!($password eq 'spice')))

print "you have entered a wrong password!";

}


##</code><code>##

# I would write that check like this:
unless (($username eq 'sugar') && ($password eq 'spice'))

# or, if you don't like unless
if(($username ne 'sugar') || ($password ne 'spice'))