Try Net::Ping in syn/ack mode. With this method you ping all the hosts in the first pass and then gather the responses in the second pass:

    # Like tcp protocol, but with many hosts
    $p = Net::Ping->new( "syn" );
    $p->port_number( getservbyname( "http", "tcp" ) );


    ### send all the pings first
    foreach $host ( @host_array ) {
      $p->ping( $host );
    }

    ### Then check which hosts responded.
    while( ( $host, $rtt, $ip ) = $p->ack ) {
      print "HOST: $host [$ip] ACKed in $rtt seconds.\n";
    }
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In this way, all the delays are overlapped and it reduces the overall runtime significantly.

It is harder to use; so read the docs carefully.