open DNS, "ping -l o -n 1 $host >nil|"||die;

##</code><code>##

open( DNS, "ping -l o -n 1 $host >nil|" ) || die $!;
# or
open DNS, "ping -l o -n 1 $host >nil|" or die $!;

##</code><code>##

open my $pipe, '-|', "ping -l o -n 1 $host" or die $!;