Authen::SASL and Net::LDAP::LDAPI

What is the right way to use SASL EXTERNAL authentication with 
Net::LDAP::LDAPI? I'm trying to do the equivalent of:

ldapwhoami -Y EXTERNAL -H ldapi:///

I tried approaches like:

$ldap->bind(undef, sasl => Authen::SASL->new(mechanism => 'EXTERNAL'));

But ended up with:

Can't locate object method "peerhost" via package "IO::Socket::UNIX" at 
/usr/local/share/perl/5.10.0/Net/LDAP.pm line 384, <DATA> line 275.

It seems that Authen::SASL doesn't like UNIX sockets. Is it a case of 
missing functionality that needs to be implemented, or is there a simple 
workaround?

Thanks,

	-Kartik