$logfile="log.txt";
$error=(/DOWN/);
$warn=(/PROBLEM/);
$redbutton="\<img src\=\'default_files/perlredblink2\.gif'>";
$greenbutton="\<img src\=\'default_files/perlgreenblink\.gif'>";
$yellowbutton="\<img src\=\'default_files/perlyellowblink\.gif'>";

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

# @logarray=<LOG>;   # dumps all of $logfile into @logarray

use strict;

# Set the button to green initially
my $button = "perlgreenblink";

# test the file line by line.
# The line gets read into $_
# I am testing on the DATA segment to illustrate the point
while (<DATA>){
    
    # test with a regex and end the 
    # while loop if there is a problem
    if (/DOWN/){
        $button = "perlredblink2";
        last;
    }
    
    if (/PROBLEM/){
        $button = "perlyellowblink";
        last;
    }
}

print "HTML for <img src=\"$button.gif\">\n";
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The while (<DATA>){ line needs to read

while (<LOG>){
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<DATA> file handle is a "special" one that points to the bit in your script following the __DATA__ marker. This is useful to demonstrate the data associated with code in a forum like this.

As suggested by others, it is good practice to close your file handle once you are finished with it.

close LOG;
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