foreach $line (0..$#file)
{
  # grab the date and dump into $date
  $date = $1 if $file[line] =~ m/^\[(.*?)\]/;

  # parse it to unix time
  $date = str2time($date); # method from Date::Parse

  # if its older than a month (30 days specifically)
  if($date < (time-2592000)) # 2592000 secs = 30 days
  { splice @file,$line,1; }
}