$user_id = '1';

TABLE USERS

usrid    firstname   lastname    country   city
------------------------

1           john       doe         uk      landon   
2           jane       deo         uk      landon


TABLE MSG

msg_id msg_from msg_to
----------------------


1      ID 1     ID 2


EXAMPLE 

msg_id msg_from msg_to
----------------------


1      ID 1 - get sender firstname and lastname and his userid from table users      ID 2


my $data = $DBH->prepare("SELECT
  msg_id,
  firstname.usrid,
  lastname.usrid AS msg_from
  
FROM
  msg
  JOIN users firstname.usrid ON msg_from = firstname.$user_id AND lastname.usrid ON msg_from = lastname.$user_id");
  
$data->execute();
$data_check = $data->fetchall_arrayref();
    foreach $data_check ( @$datainfo) {
        ($var1 #userid, $var2 #firstname, $var3 #lastname) = @$datainfo;
}


##</code><code>##


I WANT TO OUTPUT SOMETHING LIKE 


userid firstname lastname
1      John       Deo