use strict;
use warnings;
use CGI qw(standard);

my $logfile="log.txt";
my $error="DOWN";
my $warn="PROBLEM";
my $imagedir = 'default_files';
my ($redbutton, $greenbutton, $yellowbutton)
    = q(perlredblink.gif perlyellowblink.gif perlgreenblink.gif);

my $button = $greenbutton;    

print header();

open LOG, '<', $logfile or die "Cannot open $logfile for read :$!";

while (my $line = <LOG>) {
    if ($line =~ /$error/i) {
        $button = $redbutton;
        last;
    }
    elsif ($line =~ /$warn/i) {
        $button = $yellowbutton;
    }
}

close LOG;

print qq(<img src="$imagedir/$button">);