当我把我的Perl环境从5.16.0切换到5.24.0时，我得到了一个奇怪的行为，我无法理解。

use DBI;

my $conn   = 'dbi:ODBC:sqlserver_xxxx';  
my $userid = 'dw_select';  
my $passwd = 'xxxx';

for ( 1 .. 100 ) {
    warn "start try $_";
    my $dbh = DBI->connect($conn, $userid, $passwd, { RaiseError => 1 } );
    warn "end try $_";  
}

在5.16.0上运行良好，但切换到5.24.0时，得到以下结果：

start try 1 at test_con.pl line 9.
end try 1 at test_con.pl line 11.
start try 2 at test_con.pl line 9.
end try 2 at test_con.pl line 11.
start try 3 at test_con.pl line 9.
DBI connect('sqlserver_xxxx','dw_select',...) failed: 
 Unable to fetch information about the error at test_con.pl line 10.

通过这种修改，它再次无错误地运行：

use DBI;

my $conn   = 'dbi:ODBC:sqlserver_xxxx';  
my $userid = 'dw_select';  
my $passwd = 'xxxx';

my $dbh;    
for ( 1 .. 100 ) {
    warn "start try $_";
    $dbh = DBI->connect($conn, $userid, $passwd, { RaiseError => 1 } );
    warn "end try $_";  
}

你们谁能解释一下吗？