Locate the first link in the forum thread to each frame in the xkcd Time comic

find_forum_links.pl

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

use LWP::Simple;

sub main
{
    my $start = 0; 
    my %frames;
    if(open FILE, "<data/forums2.txt") {
        my $last_line;
        while(<FILE>) {
           $frames{$1} = 1 if /^(.*), (.*)$/;
           $start = $1 if $2 =~ /start=(\d*)/ && $1 > $start
        }
        close FILE or die $!;
        print "$_\n" for (keys %frames);
    }
    #print "$start\n";
    
    my $oldstart = $start;

    open FILE, ">>data/forums2.txt" or die "Couldn't open file, $!";
    my $data;
    do {
        print "\nPage: " . ($start/40+1) . "\n";
        my $time = "http://imgs.xkcd.com/comics/time/";
        my $url = "http://forums.xkcd.com/viewtopic.php?f=7&t=101043&start=$start";
        $data = get($url);

        while ($data =~ m/(#p\d*)[^#]*$time([0-9a-z]{64}\.png)/gs)
        {
            my $post = $1;
            my $img = $2;
            if (!$frames{$img}) {
                # print "$img, $url$post\n";
                print FILE "$img, $url$post\n";
                $frames{$img} = 1;
            }
        }

        $start += 40;
    } while ($start < $oldstart + 100*40 && $data =~ /$start" class="right-box right">Next/);

    close(FILE) or die $!;
}

main();