Netwallah did so in Re^3: Comparing Dates and Reoccurance.

You are not writing to the file $fh_out.

Change this line:

print "$id\t$date\t$track{$id}{COUNT}\n"
      if $prevtime and $time - $prevtime > 3600;
[download]

to this:

print $fh_out "$id\t$date\t$track{$id}{COUNT}\n"
      if $prevtime and $time - $prevtime > 3600;
[download]

Take a look at print for more information.

The proper place to follow this up was probably as a follow-up in your existing thread.