This is a quick and dirty solution, only tested with gnu last from RHEL4 so may need a bit of tweaking to suit the output of your version of last.

last comes in reverse time order already, so the first value assigned to any host will be the latest log in from that host. 

#!/usr/bin/perl
use strict;
use warnings;

my @last= `last`;
my (%time, @details, $host);

map{
   @details=split(/ +/);
   $host=$details[2];
   $time{$host}=join (' ', @details[3,4,5,6]) unless $time{$host} ;
}@last[0..$#last - 2];
map{
        print "$_, last login at $time{$_}\n";
} keys %time;

[download]

In reply to Re: Last logon and time for a system console by Utilitarian
in thread Last logon and time for a system console by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.