#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1168769

use strict;
use warnings;

my %ips;

while(<DATA>)
  {
  /.* (\S+):(\S+)$/ or next;
  $ips{$1}{$2}++;
  }

for my $who ( sort keys %ips )
  {
  print $who;
  my @ips;
  for my $ip ( @ips = sort keys %{ $ips{$who} } )
    {
    print "=> $ip ($ips{$who}{$ip})";
    }
  print $who =~ /(.*?)\@/, " total: ", scalar @ips, " unique ip's\n";
  }

__DATA__
Jul 28 13:42:27 mail vpopmail[47985]: vchkpw-smtp: (PLAIN) login success joe@example.com:192.168.250.251
Jul 28 13:42:28 mail vpopmail[47992]: vchkpw-smtp: (PLAIN) login success joe@example.com:192.168.5.23
Jul 28 13:42:29 mail vpopmail[47994]: vchkpw-smtp: (PLAIN) login success sally@example.com:192.168.10.28
Jul 28 13:42:27 mail vpopmail[47985]: vchkpw-smtp: (PLAIN) login success fred@example.com:192.168.8.8
Jul 28 13:42:28 mail vpopmail[47992]: vchkpw-smtp: (PLAIN) login success joe@example.com:192.168.5.23
Jul 28 13:42:29 mail vpopmail[47994]: vchkpw-smtp: (PLAIN) login success harry@example.com:192.168.10.5