use strict;
use warnings;

my %user;
my %conn;

while(<DATA>){
		my ($conn) = /conn=(\d+)\s/;
		my ($uid) = /uid=(.*?),/;
		$uid ? $user{$conn}=$uid : $conn{$conn}++;
}

for my $key ( keys %conn ) {
		print $user{$key}//"Unknown user";
		print ": $conn{$key} times in logfile\n";
}
__DATA__
[04/Jun/2013:13:06:13 -0600] conn=13570 op=14 msgId=13 - BIND dn="uid=xyz123,ou=People,o=xyz.com" method=128 version=3
[04/Jun/2013:15:06:13 -0600] conn=13570 op=14 msgId=15 - RESULT err=0 tag=101 nentries=48030 etime=139 SRCH=Q
[04/Jun/2013:15:06:13 -0600] conn=13570 op=14 msgId=15 - RESULT err=0 tag=101 nentries=48030 etime=139 SRCH=Q
[04/Jun/2013:15:06:13 -0600] conn=13571 op=14 msgId=15 - RESULT err=0 tag=101 nentries=48030 etime=139 SRCH=Q