your constant module should have another name, constant is already in use!

package MyConstants;
require Exporter;
@ISA = qw (Exporter);
@EXPORT_OK = qw ( LOGIN PASS IP  DB_NAME);
use constant LOGIN     => 'name';
use constant PASS     => 'pwd';
use constant IP     => '190.xxx.xxx.xx';
use constant DB_NAME     => 'mydbname';
1;
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and your code should only import the constants. No need for inherence.

use MyConstants qw/LOGIN PASS IP DB_NAME/;
DBI->connect ("DBI:mysql:host=".IP.";database=".DB_NAME."", LOGIN, PAS
+S,{PrintError => 0, RaiseError => 1})
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