Here is a snippet from some code I wrote in 2006 - hopefully this will give you an idea what to do. Note - I have not looked at this since then, and the modules may have changed.

my $SNIFF_NIC = q(\Device\NPF_{6098F1AA-BEB5-49D4-8DEC-9B08EE8CE35C});
...
my %pcap_parameters = (
        SNAPLEN => 256,         # Num bytes to capture from packet
    PROMISCUOUS_MODE => 1,  # Operate in promiscuous mode?
        TIMEOUT => 1000,        # Read timeout (ms)
        NUMPACKETS => 0,       # Pkts to read (-1 = loop forever)
        FILTER => '(ip proto \icmp) or dst port 80 or 135 or 139 or 44
+5 or 3127 or 4444',   # Filter string
    USERDATA => '',         # Passed as first arg to callback fn
    SAVEFILE => '',         # Default save file

        # Items below are RETURNED values from PCap calls.
        # Do not attempt to change them in the declaration.

        FILTER_HANDLE => 0,     # Reference to compiled filter
        NETWORK_INTERFACE => '',# Network interface to open
        NETWORK_ADDR =>0,       # Network Address (32 bit number)
        NETWORK_MASK =>0,       # Mask (32-bit number)
    mode => '',             # Internal variable
        );

.....
  $pcap_parameters{NETWORK_INTERFACE} = $SNIFF_NIC;
    ### Net::Pcap::lookupdev(\$err) or die "No Network device found:$e
+rr\n";
  if ($verbose){
    print "Requested device \t[$pcap_parameters{NETWORK_INTERFACE}]\n"
+;
    my $dev = Net::Pcap::lookupdev(\$err) 
            or die "Net::Pcap::lookupdev failed. Error was :$err;\n"; 
        print "Default device:$dev\n;";
    my ($error, %description);
       print $error if defined $error;
  }
  $result = Net::Pcap::lookupnet($pcap_parameters{NETWORK_INTERFACE},
              \$pcap_parameters{NETWORK_ADDR},
              \$pcap_parameters{NETWORK_MASK}, \$err);
  $verbose and print "Found Net \tnet " . NetPacket::IP::to_dotquad($p
+cap_parameters{NETWORK_ADDR}) .
        "  mask " . NetPacket::IP::to_dotquad($pcap_parameters{NETWORK
+_MASK}) . "\n";
....
# Signal handler
$SIG{INT} = 'KeyboardInput';
my $count = 0;
Net::Pcap::loop($pcap_desc, $pcap_parameters{NUMPACKETS}, \&process_pk
+t, "abc");
Net::Pcap::close($pcap_desc);
[download]

Yes - this was for a Windows (probably Win2003) system.