#####
#read passwd into @pwfile
####

foreach (@pwfile) {

  if (/^$old_userid:.*/) {
    $line = $_;
  }else{
    push(@new_pwfile, $_);
  }

}

($userid, $passwd, $uid, $gid, $gcos, $name, $home, $shell) = split(':', $line);

$new_line = join(':', $login, $new_passwd, $uid, $gid, $gcos, $home, $shell);

push(@new_pwfile, $new_line);

#####
#write @new_pwfile to file, swap into place
#####