I tried your script, but it got:
"Usage: Convert::Binary::C::pack(THIS, type, data = &PL_sv_undef, string = NULL) at ./p0fq.pl line 30." error

I modifed your script as:

use strict;
use warnings;

use Convert::Binary::C qw( );
use IO::Socket;
use Net::IP qw( );
use Data::Hexdumper;

use constant QUERY_MAGIC       => 0x0defaced;
use constant QTYPE_FINGERPRINT => 1;

die "usage: p0fq.pl p0f_socket src_ip src_port dst_ip dst_port"
  unless @ARGV == 5;

my $c = Convert::Binary::C->new(
           LongSize => 4,
           ShortSize => 2,
           Alignment => 4,
           ByteOrder => 'BigEndian',
);

eval { $c->parse_file("p0f-query.h") };
if ($@) {
    die "Parse error: $@";
}

# Convert the IPs and pack the request message
my $src = Net::IP->new( $ARGV[1] ) or die( Net::IP::Error() );
my $dst = Net::IP->new( $ARGV[3] ) or die( Net::IP::Error() );
print "src ip:", ($src->ip()), "\n", "dst ip:", ($dst->ip()), "\n";
my $query = $c->pack(
    'p0f_query',
    {
        magic    => QUERY_MAGIC,
        type     => QTYPE_FINGERPRINT,
        id       => 0x12345678,
        src_ad   => $src->intip(),
        dst_ad   => $dst->intip(),
        src_port => $ARGV[2],
        dst_port => $ARGV[4],
    }
);

print "query:\n", hexdump( data => $query, );

# Open the connection to p0f
my $sock = IO::Socket::UNIX->new(
    Peer => $ARGV[0],
    Type => SOCK_STREAM,
  )
  or die "Could not create socket: $!\n";
# Ask p0f
print $sock $query;
my $response = <$sock>;    # yuck!
close $sock;
print "response:\n", hexdump( data => $response, );

# Extract the response from p0f
my $data = $c->unpack( 'p0f_response', $response );
die "Bad response magic.\n"          if $data->{magic} != QUERY_MAGIC;
die "P0f did not honor our query.\n" if $data->{type} == 1;
die "This connection is not (no longer?) in the cache.\n" if $data->{t
+ype} == 2;

# Display result
print "Genre    : " . $data->{genre} . "\n";
print "Details  : " . $data->{detail} . "\n";
print "Distance : " . $data->{dist} . " hops\n";
print "Link     : " . $data->{link} . "\n";

print "Uptime   : " . $data->{uptime} . " hrs\n";
[download]

Now the running result as:

src ip:192.168.1.2
dst ip:192.168.1.1
query:
  0x0000 : 0D EF AC ED 01 00 00 00 12 34 56 78 00 00 00 00 : .........
+4Vx....
  0x0010 : 00 00 00 00 00 00 01 BB                                    
+      : ........
response:
  0x0000 : 0D EF AC ED 12 34 56 78 02 00 00 00 00 00 00 00 : .....4Vx.
+.......
  0x0010 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0020 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0030 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0040 : 00 00 00 00 00 FF 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0050 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0060 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0070 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
  0x0080 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : .........
+.......
This connection is not (no longer?) in the cache.
[download]

It is getting close, the strange thing is that the pack method seems eat up the src_ip, dst_ip, from the query hex dump, you can see src_ip and dst_ip are all 0x00, I am lost again.