use strict;
use warnings;
my $logfile="log.txt";
my $error="DOWN";
my $warn="PROBLEM";
my $redbutton="\<img src\=\'default_files/perlredblink\.gif'>";
my $greenbutton="\<img src\=\'default_files/perlgreenblink\.gif'>";
my $yellowbutton="\<img src\=\'default_files/perlyellowblink\.gif'>";
my $button = $greenbutton;
# open LOG, $logfile or die "Cannot open $logfile for read :$!";
use File::Tail;
tie *LOG, 'File::Tail', (name => $logfile, tail => -1)
    or die("log open error: $!");
while (my $line = <LOG>) {
   if ($line eq $error) { 
    $button = $redbutton; 
    print "<!--Content-type: text/html-->\n\n"; 
    print $button; 
    last; }
   elsif ($line eq $warn) { 
    $button = $yellowbutton; 
    print "<!--Content-type: text/html-->\n\n"; 
    print $button; 
    last; }
   else { 
    print "<!--Content-type: text/html-->\n\n"; 
    print $button; 
    last; }
 }
 close LOG;