use threads;

my %device_ip = ( 
    core => "3.3.3.3",
    border => "5.5.5.5",        
);

# Initialize devices' pool of threads.
my $index = 0;
my @th;
while (my ($k, $v) = each %device_ip) {
    push @th, threads->new(\&thread_job, $k, $device_ip{$k}, $index++)
}

$_->join for @th;

# Worker thread subroutine.
sub thread_job
{
    my ($dev, $ip, $i) = @_;
    my $tid = threads->tid();
    print qq![id=$tid @ $i]: IP address "$ip" corresponds to device "$dev".\n!;
}