Changes:

• Added error message if web page get fails
• Use strftime instead of backtics and Windows date symbols
• Test to see if all 3 values were found before logging
• Using Tie::File for easy read-write access to file
• Replace latest line with new data if Level has not changed
• Added error message if regex could not find all 3 values
• Replace 2 s/// with 1 tr///
• Add math and reporting of anticipated level up

use strict;
use warnings;
use LWP::Simple;
use URI::URL;
use POSIX qw/strftime/;
use Tie::File;
use DateTime;

my $date= strftime "%Y%m%d", localtime; # YYYYMMDD
my ($url, $content, $experience, $level, $posts);

$url = url('http://perlmonks.org/?node_id=844862');

$content = get($url) or die "Get failure";
$content =~ tr/\cJ\cM//d;

($experience, $level, $posts) =
        ($content =~ /Experience:\D+(\d+).+
                      Level:.+([A-Z][a-z]+\s+\(\d+\)).+
                      Writeups:.+>(\d+)</x);

die unless ($experience && $level && $posts);
my ($start, $startdt, $startexp, $today);
tie my @log, 'Tie::File', 'perl_xp.csv';
($start, $startexp) = (split ',', $log[-2])[0,1];
if ($level eq (split ',',$log[-1])[3] || '') {
    pop @log;
} 
push @log, join ',',$date,$experience,$posts,$level;
untie @log;

my ($year,$month,$day) = $start =~ m/(\d{4})(\d\d)(\d\d)/;
$startdt = DateTime->new(year => $year, month=> $month, day => $day);

($year,$month,$day) = $date =~ m/(\d{4})(\d\d)(\d\d)/;
$today = DateTime->new(year => $year, month=> $month, day => $day);
my $timeflies = $startdt->delta_days($today)->{days};
my $exprate = ($experience-$startexp)/$timeflies;
printf "%d days, %d posts, %d points, %.2f points per day\n",$timeflie
+s,$posts,$experience,$exprate;
my $nextlevel = 3000;
my $leveldays = ($nextlevel - $experience)/$exprate;
my $leveldate = $today->add(days => $leveldays);
printf "Level up in %d days, on %s\n", $leveldays, $leveldate->mdy();
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