This worked for me on Win32, AS 5.8:

use strict;
use warnings;

use IO::Socket::INET;
$|++;

my $port   = getservbyname 'bootps', 'udp'; 

print "Listening on UDP port: $port\n";
my $socket = IO::Socket::INET -> new (
    LocalPort  => $port,
        Broadcast  =>  1,
        Proto      => 'udp',
    Blocking => 1
    )
             or die "Failed to bind to socket: $@";

my $mess; 
  
while ($socket -> recv ($mess, 1024)) { 

    print "Saw: \n$mess\n";
}
[download]

... To test it, I just made a dhcp request which also uses BOOTP

c:\> ipconfig /release
c:\> ipconfig /renew
[download]

I check to be certain I was on the same lan segment as the other device sending the BOOTP request?
JamesNC
Update: I released and renewed the address on a second machine on my home network and indeed saw both the request and response. I am curious as to how to decode the DHCP message. I started to unpack the message, but I got lazy: See RFC 2131 for the message format.
Here is a link to it: RFC 2131