Try using a different string for the stored connection something like this

use strict;
use DBI;
print "Driver = $_\n" for DBI->data_sources('ODBC');

my $db_name = 'online_labs_gs'; 
my $db_type = 'MSSQL';

my %SERVER = (
  MSSQL => {
    'dsn'  => 'DBI:ODBC:MS SQL 2005',
    'user' => 'yyy',
    'pwd'  => 'yyy',
  },
  
  MSSQL1 => {
    'dsn'  => "DBI:ODBC:driver={SQL Server};server=localhost;dbq=$db_n
+ame",
    'user' => 'yyy',
    'pwd'  => 'yyy',
  },
  
  MySQL => {
    'dsn'  => "dbi:mysql:$db_name:localhost:3306",
    'user' => 'xxx',
    'pwd'  => 'xxx',
  },
);
my $hr = $SERVER{$db_type};
my $dbh = DBI->connect($hr->{'dsn'},$hr->{'user'},$hr->{'pwd'}, 
   {RaiseError => 1});
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