#!/usr/bin/perl
use strict;
use DBI;

print "DB connectivity test\n";

my $user='system';
my $password='manager';

my $DSN='dbi:Oracle://127.0.0.1:1521/db.company.local';
my $dbh = DBI->connect($DSN, $user, $password,
                      { RaiseError => 1, AutoCommit => 0 });

print "This works\n";                 
my $DSN='dbi:Oracle:host=127.0.0.1:sid=db.company.local:port=1521';
my $dbh = DBI->connect($DSN, $user, $password,
                      { RaiseError => 1, AutoCommit => 0 });
print "This doesn't\n";

##</code><code>##

DB connectivity test
This works
DBI connect('host=127.0.0.1:sid=ps.kadaster.local:port=1521','system',...) failed: ORA-12154: TNS:could not resolve the connect identifier specified (DBD ERROR:
 OCIServerAttach) at conn_test.pl line 16.