sub get_home_dir {
   return $ENV{'HOME'} unless @_;

   my ($userid) = @_;

   local *PASSWD;
   open(PASSWD, '<', '/etc/passwd')
   or die("...");

   my ($record) = 
      grep { $_->[0] eq $userid }
         map { [ split(':') ] }
            <PASSWD>;

   return $record && $record->[5];
}