If you had "use warnings" in your code, then Perl would tell you that you have opened a filehandle (USF) for writing and are then trying to read from it.

"use strict" and "use warnings" allow Perl to help you find the problems in your code. It's crazy to try and write code without them.

I don't know, would it be easier to reverse @lines?
Another programmer wrote this and I am trying work on it after the fact. And I don't know much perl..
I do appreciate the help.

You obviously have other issues with hamdling files and the words of our sage monks has given the clues there. As for reversing the order of arrays:

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

my @array1 = (1, 2, 3, 4, 5);
my @array2 = reverse( @array1 );

print join(", ", @array1), "\n";
print join(", ", @array2), "\n";

exit;
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jdtoronto

There is a way to open a file for both reading and writing (see the description of open), however, I've never used it (and a read|write open will not, according to the docs, usually work on text files). When I need to do this, I tend to use Tie::File.

One obvious thing to try is to explicitly set $count to 0 ( ($count = 0;) before starting to count the lines which are more recent than $oldest_time. Also, you may be better off using (as you said)
foreach reverse @lines
or

while(@lines){
    $timestamp = pop(@lines);
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My tendency is to prefer the latter (but not when using Tie::File!). I think the reverse will create a temporary array, while nibbling away at the end doesn't. If the files are very large, you may need to use Tie::File or File::ReadBackwards.

The next problem is that you want to read data from file and then append a new timestamp at the end. For this, you need to open the file for both reading and writing, and AFAIK call seek to swith from reading to writing. In general, calling seek will not cause more problems if it is not necessary.

my $times = 2;
my $minutes_threshold = 7200;

my $now = time();
my $oldest_time = $now - ($minutes_threshold*60);

my $user_status_file = "C:/temp/perl_logs/user_status.$user.txt";

open (USF, "+<", $user_status_file) or die "Failed to open User Status
+ File file: $!";

# Now, read through the lines of the file 
# and see if n times occured in the last m minutes.

my $count = 0;
while ( <USF> )
{
    chomp $_;
    next if ( $_ < $oldest_time );
    $count++;
}
if ( $count > $times )
{
    print ADL "User exceeded threshold! $count \n";
}
seek USF, 0, 2;      #go to the end of the file - maybe you can remove
+ this line
print  USF "$now\n";
close USF;
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perl -ne '@_=($_,@_)}{
 # file is read in @_ in reverse order
 # for (@_) loop # data manipulation ...
$count > $time and print  "exceeded threshold!";' filename
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