open(FILE, "\\\\123.456.789.10\\folder\\test.txt");

net use z: \\123.456.789.10\folder /user:test2\testuser password

use Win32::NetResource; 
 
 
my $RemoteName = "\\\\123.456.789.10\\folder"; 
 
my $RemoteShare = { 
		'Scope' => RESOURCE_CONNECTED, 
                'Type'=> RESOURCETYPE_DISK, 
                'DisplayType' => RESOURCEDISPLAYTYPE_GENERIC, 
                'Usage' => RESOURCEUSAGE_CONNECTABLE,           
                'RemoteName' => $RemoteName, 
                }; 
				 
my $UserName = "test2\\testuser"; 
 my $Password = "password"; 
 my $Connection = 0; 
  
Win32::NetResource::AddConnection($RemoteShare,$Password,$UserName,$Connection) 
  or print "unable to connect to the network\n"; 
 
open(FILE, "$RemoteName\\test.txt");