Looks like it DID work. You successfully pinged 12 hosts.

To get the "verbose" output, run it like this:
>ping_sweep2.pl -v

     Re:Do I have to convert the hostnames to IP address first?Any

From the Net::Ping FM:
$host can be either the hostname or the IP number of the remote host

You should also be able to collapse some of the code like so (untested):

##Replace THIS code 
while (<DATA>)
{
   chomp;
   print "$_ : ";
   my $ip_address = Win32::AdminMisc::gethostbyname($_);
   print "$ip_address\n";
   push (@targets, $ip_address);
}

# Generate list of hosts to ping
foreach my $target (@targets) 
{
  $RequestQ->enqueue ($target);
}


## Replace with THIS code ####
while (<DATA>)
{
   chomp;
   print "Queuing ping for $_ : ";
   $RequestQ->enqueue $_ ; # Feed the NAME directly in
}
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