I'll admit that it took me a while to figure out what these constructions were doing

$uid = ${$entry->get('uid')}[0] if defined $entry->get('uid');
# and
$uids{$uid}{$_} = ${$entry->get($_)}[0] if defined $entry->get($_);
[download]

I think using a temporary var to hold the array reference is preferable to calling the function twice. It also simplifies and clarifies (IMO) the code.

for my $entry ( $searchresult->entries ) {
    my $aref = $entry->get( 'uid' );
    my $uid = $aref->[0] if $aref;

    if( $uid ) {
        for ( @vars ) {
            $aref = $entry->get( $_ );
            $uids{ $uid }{ $_ } = $aref->[0] if defined $aref;
        }
    } 
    else {
        print "*** No uid for the following  entry:\n";
        print Dumper( \$entry );
    }
}
[download]

I have also come to prefer a little more whitespace inside parens, curlies and the like, but that a very personal thing.